Edwards Syndrome (Trisomy 18)
Overview Definition Edwards syndrome, or trisomy 18, is defined as the presence of 3 copies of chromosome 18. Epidemiology Etiology Mnemonic Mnemonic for Edwards syndrome (trisomy 18): “At 18 you can vote in an election.” Pathophysiology Genetics Nondisjunction Translocation Mosaicism Clinical Presentation Diagnosis and Prognosis Maternal screening Table: Maternal screening 1st and 2nd trimesters 1st […]
Primary Ciliary Dyskinesia
Overview Definition Primary ciliary dyskinesia (PCD) is a genetic condition in which cilia in the respiratory tract have defective functionality that leads to ineffective mucociliary clearance. Epidemiology Etiology Pathophysiology Normal physiology Ciliary dysfunction Clinical Presentation Onset Signs and symptoms Other related findings Diagnosis Evaluation of ciliary function There is no gold standard diagnostic test for […]
Prader-Willi Syndrome and Angelman Syndrome
Overview Definitions Prader-Willi syndrome (PWS) is a condition associated with loss of the paternal chromosome 15q11-13 region and is characterized by intellectual disability, short stature, underdevelopment of the sexual organs, and obesity. Angelman syndrome (AS) is a disorder associated with loss of the maternal chromosome 15q11-13 region and is characterized by severe neurodevelopmental delay. Epidemiology […]
Down syndrome (Trisomy 21)
Epidemiology and Genetics Epidemiology Genetics There are 3 genotypes that result in Down syndrome. Clinical Presentation Craniofacial Ocular High prevalence of ocular disorders: Frequency increases with age. Auditory Musculoskeletal Cardiovascular Gastrointestinal Hematologic Endocrine Reproductive Neurologic Psychiatric/behavioral Development Other associated conditions Diagnosis Prenatal diagnosis Screening is recommended prior to 20th week of gestation. Postnatal diagnosis Management […]
Androgen Insensitivity Syndrome
Overview Epidemiology Genetics Pathophysiology Classification Sexual characteristics of affected individuals can vary and lead to 1 of the 3 classification types: Clinical Presentation Complete androgen insensitivity syndrome Partial androgen insensitivity syndrome Mild androgen insensitivity syndrome Diagnosis Management Clinical Relevance Differential diagnosis All disorders affecting sexual development must be considered. The following are select conditions that […]
Congenital Adrenal Hyperplasia
Epidemiology and Genetics Epidemiology Genetics Congenital adrenal hyperplasia comprises a spectrum of disorders in which different gene mutations cause different enzyme deficiencies affecting steroid biogenesis, which is carried out by the adrenal glands. Pathophysiology Normal adrenal hormone synthesis Impaired hormone synthesis in CAH 21-hydroxylase deficiency 11β-hydroxylase deficiency 17α-hydroxylase deficiency P450 oxidoreductase deficiency 3β-hydroxysteroid dehydrogenase deficiency […]
Ovotesticular Disorder of Sexual Development (ODSD)
Overview Epidemiology Genetics Pathophysiology Ovotesticular disorder of sexual development (ODSD) is characterized by the presence of gonads that contain ovarian tissue with primordial follicles and testicular tissue with seminiferous tubules in the same individual. An affected person may have: The type of internal genitalia present depends on the adjacent gonad: Clinical Presentation Female individuals (46,XX) […]
Zellweger Syndrome
Epidemiology and Genetics Epidemiology Genetics Clinical Presentation Clinical manifestations of ZWS are present at birth. Craniofacial dysmorphism Neurologic abnormalities Ocular abnormalities Hepatic abnormalities Renal abnormalities Associated conditions Diagnosis and Management Diagnosis Management There is no cure and no effective treatment for ZWS. Treatment is supportive at best. Prognosis Death typically occurs within 1 year of […]
Aromatase Deficiency
Overview Epidemiology Genetics Pathophysiology Clinical Presentation Clinical Phenotype Associated conditions Diagnosis and Management Diagnosis Management Differential Diagnosis References
Kallmann Syndrome
Overview Epidemiology Genetics Pathophysiology The genes listed above are involved in the migration of olfactory neurons and neurons involved in gonadotropin-releasing hormone (GnRH) production to their proper functional place in the brain during development. Clinical Presentation The clinical presentation is highly variable due to the different gene mutations and penetrance levels. However, all individuals with […]