Turner Syndrome

Epidemiology and Genetics

Epidemiology

• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 1 in 2,000–2,500 live births 
• 99% spontaneously abort
• Most frequent gonadal chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics anomaly in women

Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics

• Karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System: Only 1 normal X chromosome X chromosome The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in human and other male-heterogametic species. Basic Terms of Genetics is present; the other is missing or impaired.
  • Complete sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria chromosomal monosomy Monosomy The condition in which one chromosome of a pair is missing. In a normally diploid cell it is represented symbolically as 2n-1. Types of Mutations in approximately 45% of live births: 45,X0 (2nd sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics is missing)
  • Sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria chromosomal mosaicism Mosaicism The occurrence in an individual of two or more cell populations of different chromosomal constitutions, derived from a single zygote, as opposed to chimerism in which the different cell populations are derived from more than one zygote. Chromosome Testing in approximately 50% of live births:
    • Most commonly 46,XX with 45,X0
    • Approximately 10%–12% have mosaicism Mosaicism The occurrence in an individual of two or more cell populations of different chromosomal constitutions, derived from a single zygote, as opposed to chimerism in which the different cell populations are derived from more than one zygote. Chromosome Testing involving Y chromosome Y chromosome The male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans and in some other male-heterogametic species in which the homologue of the X chromosome has been retained. Basic Terms of Genetics material.
• Etiology: 
  • The underlying process is nondisjunction Nondisjunction The failure of homologous chromosomes or chromatids to segregate during mitosis or meiosis with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. Basic Terms of Genetics, which may occur during meiosis Meiosis The creation of eukaryotic gametes involves a DNA replication phase followed by 2 cellular division stages: meiosis I and meiosis II. Meiosis I separates homologous chromosomes into separate cells (1n, 2c), while meiosis II separates sister chromatids into gametes (1n, 1c). Meiosis or mitosis Mitosis A type of cell nucleus division by means of which the two daughter nuclei normally receive identical complements of the number of chromosomes of the somatic cells of the species. Cell Cycle:
    • In meiosis Meiosis The creation of eukaryotic gametes involves a DNA replication phase followed by 2 cellular division stages: meiosis I and meiosis II. Meiosis I separates homologous chromosomes into separate cells (1n, 2c), while meiosis II separates sister chromatids into gametes (1n, 1c). Meiosis: Failure of chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure ( meiosis I Meiosis I Following DNA replication, meiosis I creates 2 daughter cells containing half the genetic information of the mother cell (1n) but the same number of chromosomes (2c) by segregating sister chromatids into the same daughter cell Meiosis) or chromatids ( meiosis II Meiosis II Meiosis II is a cellular division event wherein the number of chromosomes in the daughter cells is halved from that of the mother cell. Meiosis II: similar to meiosis I but not preceded by interphase (DNA replication) Meiosis) to separate leads to loss of a chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics (chromosomal monosomy Monosomy The condition in which one chromosome of a pair is missing. In a normally diploid cell it is represented symbolically as 2n-1. Types of Mutations). 
    • In mitosis Mitosis A type of cell nucleus division by means of which the two daughter nuclei normally receive identical complements of the number of chromosomes of the somatic cells of the species. Cell Cycle: Postzygotic nondisjunction Nondisjunction The failure of homologous chromosomes or chromatids to segregate during mitosis or meiosis with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. Basic Terms of Genetics leads to different cells within the same individual containing different chromosomal content/karyotypes (chromosomal mosaicism Mosaicism The occurrence in an individual of two or more cell populations of different chromosomal constitutions, derived from a single zygote, as opposed to chimerism in which the different cell populations are derived from more than one zygote. Chromosome Testing).
  • Nearly 70% of cases are due to meiotic nondisjunction Nondisjunction The failure of homologous chromosomes or chromatids to segregate during mitosis or meiosis with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. Basic Terms of Genetics of paternal sex chromosomes Sex chromosomes The homologous chromosomes that are dissimilar in the heterogametic sex. There are the X chromosome, the Y chromosome, and the w, z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth bombyx mori, for example)). In such cases the w chromosome is the female-determining and the male is zz. Basic Terms of Genetics; i.e., the paternal X chromosome X chromosome The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in human and other male-heterogametic species. Basic Terms of Genetics is lost.
• No known risk factors

Clinical Presentation

Clinical phenotype Phenotype The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics

• Outer appearance
  • Short stature
  • Pterygium colli (webbed neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess)
  • Congenital Congenital Chorioretinitis lymphedema Lymphedema Edema due to obstruction of lymph vessels or disorders of the lymph nodes. Lymphatic Filariasis (Elephantiasis)
  • “Shield chest”: broad chest with widely spaced nipples
  • Lymphedema Lymphedema Edema due to obstruction of lymph vessels or disorders of the lymph nodes. Lymphatic Filariasis (Elephantiasis) on the back of the hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and foot Foot The foot is the terminal portion of the lower limb, whose primary function is to bear weight and facilitate locomotion. The foot comprises 26 bones, including the tarsal bones, metatarsal bones, and phalanges. The bones of the foot form longitudinal and transverse arches and are supported by various muscles, ligaments, and tendons. Foot: Anatomy (sausage-like appearance of fingers and toes)
  • Low hairline
  • Cubitus valgus (outward-turned forearms Forearms Part of the upper extremity in humans and primates extending from the elbow to the wrist. Bowen Disease and Erythroplasia of Queyrat)
  • Multiple ( benign Benign Fibroadenoma) pigment nevi Nevi Nevi (singular nevus), also known as “moles,” are benign neoplasms of the skin. Nevus is a non-specific medical term because it encompasses both congenital and acquired lesions, hyper- and hypopigmented lesions, and raised or flat lesions. Nevus/Nevi
  • Ear anomalies such as low-set or rotated ears
  • Nail dysplasias
  • Short 4th metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy/metatarsals
  • Kyphosis Kyphosis Deformities of the spine characterized by an exaggerated convexity of the vertebral column. The forward bending of the thoracic region usually is more than 40 degrees. This deformity sometimes is called round back or hunchback. Osteoporosis and/or scoliosis Scoliosis Scoliosis is a structural alteration of the vertebral column characterized by a lateral spinal curvature of greater than 10 degrees in the coronal plane. Scoliosis can be classified as idiopathic (in most cases) or secondary to underlying conditions. Scoliosis
• Cognition/intelligence
  • Intelligence can be normal or reduced.
  • A deficit in some areas can be present (e.g., mathematics, spatial orientation Spatial orientation Change in position or alignment in response to an external stimulus. Psychiatric Assessment).
• Behavioral phenotype Phenotype The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics
  • Increased risk of impaired social skills and/or mood disorders such as anxiety Anxiety Feelings or emotions of dread, apprehension, and impending disaster but not disabling as with anxiety disorders. Generalized Anxiety Disorder or depression
• Sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria development/fertility
  • Hypergonadotropic hypogonadism Hypergonadotropic Hypogonadism Hypogonadism
    • Primary ovarian failure as development of ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy typically impaired (streak gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types)
    • Decreased estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy and progesterone Progesterone The major progestational steroid that is secreted primarily by the corpus luteum and the placenta. Progesterone acts on the uterus, the mammary glands and the brain. It is required in embryo implantation; pregnancy maintenance, and the development of mammary tissue for milk production. Progesterone, converted from pregnenolone, also serves as an intermediate in the biosynthesis of gonadal steroid hormones and adrenal corticosteroids. Gonadal Hormones levels with elevated luteinizing hormone ( LH LH A major gonadotropin secreted by the adenohypophysis. Luteinizing hormone regulates steroid production by the interstitial cells of the testis and the ovary. The preovulatory luteinizing hormone surge in females induces ovulation, and subsequent luteinization of the follicle. Luteinizing hormone consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity. Menstrual Cycle) and follicle-stimulating hormone ( FSH FSH A major gonadotropin secreted by the adenohypophysis. Follicle-stimulating hormone stimulates gametogenesis and the supporting cells such as the ovarian granulosa cells, the testicular sertoli cells, and leydig cells. Fsh consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity. Menstrual Cycle)
  • Delayed or lack of onset of puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty due to lack of estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy
    • Lack of breast development
    • Primary amenorrhea Amenorrhea Absence of menstruation. Congenital Malformations of the Female Reproductive System
  • Infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility
    • Spontaneous pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care very unlikely, but possible in 2%–5% of affected persons

Associated conditions

• Cardiac abnormalities:
  • Found in approximately ⅓ of individuals with Turner syndrome
  • Congenital Congenital Chorioretinitis bicuspid aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy → ↑ risk of aortic stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS) and/or aortic insufficiency
  • Congenital coarctation of the aorta Congenital Coarctation of The Aorta Coarctation of the Aorta (abnormal narrowing in segment of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy) 
  • Anomalies of the pulmonary veins Pulmonary veins The veins that return the oxygenated blood from the lungs to the left atrium of the heart. Lungs: Anatomy
  • ↑ Risk of aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection (tear occurs in the inner layer of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy) or rupture; risk goes up during pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
• Malformations of the kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy and ureters Ureters One of a pair of thick-walled tubes that transports urine from the kidney pelvis to the urinary bladder. Urinary Tract: Anatomy
  • Horseshoe kidneys Horseshoe Kidneys Imaging of the Urinary System (normal functioning kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy congenitally fused, forming a horseshoe shape)
  • Agenesis Agenesis Teratogenic Birth Defects, rotational anomalies, obstructions
• Vision Vision Ophthalmic Exam impairments such as color blindness Blindness The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of eye diseases; optic nerve diseases; optic chiasm diseases; or brain diseases affecting the visual pathways or occipital lobe. Retinopathy of Prematurity, cataracts, and strabismus Strabismus Strabismus is the misalignment of the eyes while fixating the gaze on an object. Strabismus can be idiopathic, but it may also be caused by cerebral palsy, uncorrected refractive errors, and extraocular muscle or cranial nerve dysfunction. Strabismus (crossed eyes)
• Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
• Cystic Cystic Fibrocystic Change hygroma (abnormal growth/ mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast, typically on the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess)
• Hearing loss Hearing loss Hearing loss, also known as hearing impairment, is any degree of impairment in the ability to apprehend sound as determined by audiometry to be below normal hearing thresholds. Clinical presentation may occur at birth or as a gradual loss of hearing with age, including a short-term or sudden loss at any point. Hearing Loss
• Recurrent otitis media
• Celiac disease Celiac disease Celiac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis. Celiac Disease
• Osteoporosis Osteoporosis Osteoporosis refers to a decrease in bone mass and density leading to an increased number of fractures. There are 2 forms of osteoporosis: primary, which is commonly postmenopausal or senile; and secondary, which is a manifestation of immobilization, underlying medical disorders, or long-term use of certain medications. Osteoporosis and pathologic fractures secondary to ↓ estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy levels
• ↑ Risk of gonadoblastoma if Y chromosome Y chromosome The male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans and in some other male-heterogametic species in which the homologue of the X chromosome has been retained. Basic Terms of Genetics material present

Diagnosis and Management

Diagnosis

• If suspected in utero:
  • Chorionic villi sampling Chorionic villi sampling A method for diagnosis of fetal diseases by sampling the cells of the placental chorionic villi for DNA analysis, presence of bacteria, concentration of metabolites, etc. The advantage over amniocentesis is that the procedure can be carried out in the first trimester. Congenital TORCH Infections (CVS)
  • Amniocentesis Amniocentesis Percutaneous transabdominal puncture of the uterus during pregnancy to obtain amniotic fluid. It is commonly used for fetal karyotype determination in order to diagnose abnormal fetal conditions. Polyhydramnios with karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System 
• Postnatal diagnosis:
  • History and clinical examination
  • Genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies: Karyotyping Karyotyping Mapping of the karyotype of a cell. Chromosome Testing confirms the diagnosis.
  • Labs show: ↓ estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy and androgen levels, ↑ LH LH A major gonadotropin secreted by the adenohypophysis. Luteinizing hormone regulates steroid production by the interstitial cells of the testis and the ovary. The preovulatory luteinizing hormone surge in females induces ovulation, and subsequent luteinization of the follicle. Luteinizing hormone consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity. Menstrual Cycle and FSH FSH A major gonadotropin secreted by the adenohypophysis. Follicle-stimulating hormone stimulates gametogenesis and the supporting cells such as the ovarian granulosa cells, the testicular sertoli cells, and leydig cells. Fsh consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity. Menstrual Cycle levels
• Additional screening Screening Preoperative Care tests once diagnosis is confirmed:
  • Hearing evaluation
  • Eye exam
  • Neuropsychological, developmental, educational, and behavioral assessments/screenings 
  • Blood pressure measurements in arms and legs
  • Routine labs: thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy test, lipid screening Screening Preoperative Care, glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance screening Screening Preoperative Care, liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes
  • Imaging:
    • Baseline echocardiogram Echocardiogram Transposition of the Great Vessels and/or cardiac magnetic resonance Cardiac magnetic resonance Aortic Regurgitation imaging (MRI) to check for cardiac defects
    • Renal ultrasound to check for malformations
    • Baseline dual-energy X-ray absorptiometry Dual-Energy X-Ray Absorptiometry Osteoporosis ( DEXA DEXA Osteoporosis) scan in early adulthood

Management

• Hormonal replacement:
  • Estrogen therapy Estrogen therapy The use of hormonal agents with estrogen-like activity in postmenopausal or other estrogen-deficient women to alleviate effects of hormone deficiency, such as vasomotor symptoms, dyspareunia, and progressive development of osteoporosis. This may also include the use of progestational agents in combination therapy. Menopause (life long) initiated in adolescence for sexual maturation/development
  • Cyclic progestin therapy to accompany estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy within 2 years of beginning estrogen therapy Estrogen therapy The use of hormonal agents with estrogen-like activity in postmenopausal or other estrogen-deficient women to alleviate effects of hormone deficiency, such as vasomotor symptoms, dyspareunia, and progressive development of osteoporosis. This may also include the use of progestational agents in combination therapy. Menopause and/or breakthrough bleeding begins
  • Human growth hormone Human growth hormone A 191-amino acid polypeptide hormone secreted by the human adenohypophysis, also known as gh or somatotropin. Synthetic growth hormone, termed somatropin, has replaced the natural form in therapeutic usage such as treatment of dwarfism in children with growth hormone deficiency. Idiopathic Intracranial Hypertension to try to improve short stature; used until bone age Bone Age Short Stature in Children reaches 14 years
• Fertility treatment if children are desired
• In the rare instance of Y chromosome Y chromosome The male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans and in some other male-heterogametic species in which the homologue of the X chromosome has been retained. Basic Terms of Genetics material being present, gonadectomy is recommended.

Clinical Relevance

Differential diagnosis

The following conditions are differential diagnoses of Turner syndrome:

• Noonan syndrome Noonan syndrome A genetically heterogeneous, multifaceted disorder characterized by short stature, webbed neck, ptosis, skeletal malformations, hypertelorism, hormonal imbalance, cryptorchidism, multiple cardiac abnormalities (most commonly including pulmonary valve stenosis), and some degree of intellectual disability. The phenotype bears similarities to that of turner syndrome that occurs only in females and has its basis in a 45, X karyotype abnormality. Noonan syndrome occurs in both males and females with a normal karyotype (46, XX and 46, xy). Mutations in a several genes (ptpn11, kras, sos1, nf1 and raf1) have been associated the ns phenotype. Mutations in ptpn11 are the most common. Leopard syndrome, a disorder that has clinical features overlapping those of noonan syndrome, is also due to mutations in ptpn11. In addition, there is overlap with the syndrome called neurofibromatosis-noonan syndrome due to mutations in nf1. Hypogonadism: autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance genetic condition caused by several potential gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics mutations. Both men and women can be affected. Clinical presentation includes short stature, webbed neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, and congenital Congenital Chorioretinitis heart defects. Genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies confirms the diagnosis. Individuals with Noonan syndrome Noonan syndrome A genetically heterogeneous, multifaceted disorder characterized by short stature, webbed neck, ptosis, skeletal malformations, hypertelorism, hormonal imbalance, cryptorchidism, multiple cardiac abnormalities (most commonly including pulmonary valve stenosis), and some degree of intellectual disability. The phenotype bears similarities to that of turner syndrome that occurs only in females and has its basis in a 45, X karyotype abnormality. Noonan syndrome occurs in both males and females with a normal karyotype (46, XX and 46, xy). Mutations in a several genes (ptpn11, kras, sos1, nf1 and raf1) have been associated the ns phenotype. Mutations in ptpn11 are the most common. Leopard syndrome, a disorder that has clinical features overlapping those of noonan syndrome, is also due to mutations in ptpn11. In addition, there is overlap with the syndrome called neurofibromatosis-noonan syndrome due to mutations in nf1. Hypogonadism have a normal karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System. Developmental delays are more common than in Turner syndrome. 
• Gonadal dysgenesis Gonadal dysgenesis A number of syndromes with defective gonadal developments such as streak gonads and dysgenetic testes or ovaries. The spectrum of gonadal and sexual abnormalities is reflected in their varied sex chromosome (sex chromosomes) constitution as shown by the karyotypes of 45, X monosomy (Turner syndrome); 46, XX (gonadal dysgenesis, 46xx); 46, XY (gonadal dysgenesis, 46, xy); and sex chromosome mosaicism. Their phenotypes range from female, through ambiguous, to male. This concept includes gonadal agenesis. Wilms Tumor: congenital Congenital Chorioretinitis condition in which the gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types do not develop. Both men and women are affected. Gonadal dysgenesis Gonadal dysgenesis A number of syndromes with defective gonadal developments such as streak gonads and dysgenetic testes or ovaries. The spectrum of gonadal and sexual abnormalities is reflected in their varied sex chromosome (sex chromosomes) constitution as shown by the karyotypes of 45, X monosomy (Turner syndrome); 46, XX (gonadal dysgenesis, 46xx); 46, XY (gonadal dysgenesis, 46, xy); and sex chromosome mosaicism. Their phenotypes range from female, through ambiguous, to male. This concept includes gonadal agenesis. Wilms Tumor is not caused by a chromosomal abnormality. Women have a normal 46,XX karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System with lack of onset of puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty, primary amenorrhea Amenorrhea Absence of menstruation. Congenital Malformations of the Female Reproductive System, and infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility similar to Turner syndrome. The phenotypic features seen in Turner syndrome are not present, however. Therapy with hormone replacement is required.

Related condition

The following condition is related to Turner syndrome as it also causes gonadal insufficiency due to a chromosomal abnormality:

• Klinefelter syndrome Klinefelter syndrome Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of congenital hypogonadism. Klinefelter Syndrome: chromosomal abnormality disorder seen in men in which extra X and possibly Y chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure are present in karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System. Causes delayed puberty Delayed Puberty Delayed puberty (DP) is defined as the lack of testicular growth in boys past the age of 14 and the lack of thelarche in girls past the age of 13. Delayed puberty affects up to 5% of healthy boys and girls, and half of all cases are due to constitutional growth delay. Delayed Puberty and primary hypergonadotropic hypogonadism Hypergonadotropic Hypogonadism Hypogonadism in men. Individuals with this condition tend to present as tall, phenotypic men, with small testes Testes Gonadal Hormones, decreased body hair, gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia, and infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility. Genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies confirms the diagnosis. Requires testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens replacement therapy.