Malassezia Fungi

General Characteristics and Epidemiology

General features of Malassezia

• Formerly known as Pityrosporum
• Taxonomy:
  • Family: Malasseziaceae
  • Genus: Malassezia
• Dimorphic:
  • Yeast Yeast A general term for single-celled rounded fungi that reproduce by budding. Brewers’ and bakers’ yeasts are saccharomyces cerevisiae; therapeutic dried yeast is yeast, dried. Mycology: spherical or oval
  • Mycelial form: short hyphae Hyphae Microscopic threadlike filaments in fungi that are filled with a layer of protoplasm. Collectively, the hyphae make up the mycelium. Mycology
• Colonies are cream or yellowish in color.
• Lipophilic
• Most species are lipid-dependent.
• Not a dermatophyte
• Reproduce by unipolar Unipolar Nervous System: Histology budding Budding Mycology

Clinically relevant species

There are a number of recognized species:

• M. furfur (most common)
• M. globosa (common)
• M. caprae
• M. cuniculi
• M. dermatis
• M. equina
• M. japonica
• M. nana
• M. obtusa
• M. pachydermatis
• M. psittaci
• M. restricta
• M. slooffiae
• M. sympodialis
• M. yamatoensis

Associated diseases

• Tinea (pityriasis) versicolor
• Seborrheic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema)
• Malassezia folliculitis
• Catheter-associated fungemia Fungemia The presence of fungi circulating in the blood. Opportunistic fungal sepsis is seen most often in immunosuppressed patients with severe neutropenia or in postoperative patients with intravenous catheters and usually follows prolonged antibiotic therapy. Chronic Granulomatous Disease
• Meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis
• Septic arthritis Septic arthritis Septic arthritis is an infection of the joint due to direct inoculation, contiguous extension, or hematogenous spread of infectious organisms into the joint space. This process causes an acute, inflammatory, monoarticular arthritis. Septic Arthritis
• Peritonitis Peritonitis Inflammation of the peritoneum lining the abdominal cavity as the result of infectious, autoimmune, or chemical processes. Primary peritonitis is due to infection of the peritoneal cavity via hematogenous or lymphatic spread and without intra-abdominal source. Secondary peritonitis arises from the abdominal cavity itself through rupture or abscess of intra-abdominal organs. Penetrating Abdominal Injury
• Urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease

Epidemiology

Tinea versicolor:

• Highest 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 in tropical climates and summer months
• More common in adults (ages 20–50 years)

Malassezia folliculitis:

• Common in hot, humid environments
• More common in adolescents and young adults (ages 13–45 years)

Pathogenesis

Reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli

Malassezia are part of the normal skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions flora in humans and animals Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, animalia was one of the kingdoms. Under the modern three domain model, animalia represents one of the many groups in the domain eukaryota. Cell Types: Eukaryotic versus Prokaryotic.

Host risk factors

Predisposing risk factors for disease include:

• Genetic predisposition
• Warm, humid environments
• Immunosuppression:
  • Steroid use
  • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
  • Hematologic malignancy Malignancy Hemothorax
  • Organ transplantation Organ Transplantation Transplantation is a procedure that involves the removal of an organ or living tissue and placing it into a different part of the body or into a different person. Organ transplantations have become the therapeutic option of choice for many individuals with end-stage organ failure. Organ Transplantation
• Malnutrition Malnutrition Malnutrition is a clinical state caused by an imbalance or deficiency of calories and/or micronutrients and macronutrients. The 2 main manifestations of acute severe malnutrition are marasmus (total caloric insufficiency) and kwashiorkor (protein malnutrition with characteristic edema). Malnutrition in children in resource-limited countries
• Excessive sebum production Excessive Sebum Production Acne Vulgaris
• Hyperhidrosis
• Neonates (catheter-associated infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease)

Pathophysiology

Tinea versicolor:

• Malassezia conversion to pathogenic mycelial form → overgrowth in stratum corneum Stratum corneum Skin: Structure and Functions → degradation of lipids Lipids Lipids are a diverse group of hydrophobic organic molecules, which include fats, oils, sterols, and waxes. Fatty Acids and Lipids → azelaic acid Azelaic Acid Acne Vulgaris production → inhibition of tyrosinase and melanocyte damage → hypopigmentation and scaling
• Inflammatory response → hyperpigmentation and/or pink discoloration

Seborrheic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema):

• Exact pathophysiologic mechanism remains unknown.
• Malassezia cleave fatty acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance from sebum Sebum The oily substance secreted by sebaceous glands. It is composed of keratin, fat, and cellular debris. Infectious Folliculitis → release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology inflammatory free fatty acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance
• Aberrant keratinocyte Keratinocyte Epidermal cells which synthesize keratin and undergo characteristic changes as they move upward from the basal layers of the epidermis to the cornified (horny) layer of the skin. Successive stages of differentiation of the keratinocytes forming the epidermal layers are basal cell, spinous or prickle cell, and the granular cell. Erythema Multiforme production → abnormal stratum corneum Stratum corneum Skin: Structure and Functions → inflammatory response stimulated → skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions eruption
• Other factors may include oxidative stress Oxidative stress A disturbance in the prooxidant-antioxidant balance in favor of the former, leading to potential damage. Indicators of oxidative stress include damaged DNA bases, protein oxidation products, and lipid peroxidation products. Cell Injury and Death and cell-damaging oxygen radicals.

Malassezia folliculitis:

• Plugging of a hair follicle Hair follicle A tube-like invagination of the epidermis from which the hair shaft develops and into which sebaceous glands open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. Follicles of very long hairs extend into the subcutaneous layer of tissue under the skin. Cowden Syndrome → sebaceous environment for yeast Yeast A general term for single-celled rounded fungi that reproduce by budding. Brewers’ and bakers’ yeasts are saccharomyces cerevisiae; therapeutic dried yeast is yeast, dried. Mycology growth
• Degradation of lipids Lipids Lipids are a diverse group of hydrophobic organic molecules, which include fats, oils, sterols, and waxes. Fatty Acids and Lipids → inflammatory fatty acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance → inflammatory response

Clinical Presentation and Diagnosis

Tinea versicolor

Symptoms:

• Generally asymptomatic, but mild pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema) can occur
• Evolving rash Rash Rocky Mountain Spotted Fever
• Affected areas do not tan (often noted during summer months).

Physical exam:

• Rash Rash Rocky Mountain Spotted Fever appearance:
  • Numerous well-demarcated oval or round lesions
  • Macules, plaques, or patches Patches Vitiligo
  • Scaly
  • Hypopigmented, hyperpigmented, or pink
• Distribution: 
  • Chest
  • Back
  • Abdomen
  • Face
  • Neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess

Seborrheic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema)

• Moderate to severe pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema)
• Appearance:
  • Erythematous papules and plaques
  • Thick, greasy scales Scales Dry or greasy masses of keratin that represent thickened stratum corneum. Secondary Skin Lesions
  • Yellow crust Crust Dried exudate of body fluids (blood, pus, or sebum) on an area of damaged skin Secondary Skin Lesions
• Distribution:
  • Scalp
  • Eyebrows
  • Mustache/beard area
  • Nasolabial folds
  • Upper chest and back
  • Intertriginous areas

Malassezia folliculitis

This condition may appear similar to acne vulgaris Acne vulgaris Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne Vulgaris or bacterial folliculitis:

• Monomorphic, erythematous papules or pustules
• Follicular pattern
• Pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema)
• Distribution:
  • Back
  • Upper arms
  • Chest
  • Neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess
  • Forehead Forehead The part of the face above the eyes. Melasma
  • Chin Chin The anatomical frontal portion of the mandible, also known as the mentum, that contains the line of fusion of the two separate halves of the mandible (symphysis menti). This line of fusion divides inferiorly to enclose a triangular area called the mental protuberance. On each side, inferior to the second premolar tooth, is the mental foramen for the passage of blood vessels and a nerve. Melasma
  • Sides of the face

Diagnosis

The diagnosis is most often made clinically on the basis of the history and examination. Additional evaluation can include:

• Visualization with Wood’s lamp:
  • Yellow to yellow-green fluorescence
  • Seen in only ⅓ of cases
• Microscopy:
  • Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions scraping with KOH preparation KOH preparation Primary Skin Lesions
  • “Spaghetti and meatballs” appearance of hyphae Hyphae Microscopic threadlike filaments in fungi that are filled with a layer of protoplasm. Collectively, the hyphae make up the mycelium. Mycology and spores Spores The reproductive elements of lower organisms, such as bacteria; fungi; and cryptogamic plants. Anthrax
• Cultures may be obtained for invasive disease (e.g., meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis, septic arthritis Septic arthritis Septic arthritis is an infection of the joint due to direct inoculation, contiguous extension, or hematogenous spread of infectious organisms into the joint space. This process causes an acute, inflammatory, monoarticular arthritis. Septic Arthritis).

Management and Prevention

Management

• Topical antifungals:
  • Selenium Selenium An element with the atomic symbol se, atomic number 34, and atomic weight 78. 97. It is an essential micronutrient for mammals and other animals but is toxic in large amounts. Selenium protects intracellular structures against oxidative damage. It is an essential component of glutathione peroxidase. Trace Elements sulfide shampoo
  • Zinc Zinc A metallic element of atomic number 30 and atomic weight 65. 38. It is a necessary trace element in the diet, forming an essential part of many enzymes, and playing an important role in protein synthesis and in cell division. Zinc deficiency is associated with anemia, short stature, hypogonadism, impaired wound healing, and geophagia. It is known by the symbol zn. Trace Elements pyrithione shampoo
  • Ketoconazole Ketoconazole Broad spectrum antifungal agent used for long periods at high doses, especially in immunosuppressed patients. Azoles cream or shampoo
  • Miconazole Miconazole An imidazole antifungal agent that is used topically and by intravenous infusion. Azoles
  • Terbinafine Terbinafine In addition to the 3 other major classes of antifungal agents (azoles, polyenes, and echinocandins), several other clinically important antifungal agents are used, including flucytosine, griseofulvin, and terbinafine. Terbinafine acts within the stratum corneum of the skin and are used to treat dermatophyte infections of the skin, hair, and nails. Flucytosine, Griseofulvin, and Terbinafine
• Oral antifungal Antifungal Azoles (for widespread, recurrent, invasive, or refractory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease):
  • Fluconazole Fluconazole Triazole antifungal agent that is used to treat oropharyngeal candidiasis and cryptococcal meningitis in aids. Azoles
  • Itraconazole Itraconazole A triazole antifungal agent that inhibits cytochrome p-450-dependent enzymes required for ergosterol synthesis. Azoles
  • Voriconazole Voriconazole A triazole antifungal agent that specifically inhibits sterol 14-alpha-demethylase and cytochrome p-450 cyp3a. Azoles
  • Amphotericin B Amphotericin B Macrolide antifungal antibiotic produced by streptomyces nodosus obtained from soil of the orinoco river region of venezuela. Polyenes (for severe, invasive disease)

Prevention

Recurrences of tinea versicolor and seborrheic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema) can be prevented with topical antifungal Antifungal Azoles prophylaxis Prophylaxis Cephalosporins.

Differential Diagnosis

• Atopic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema): chronic, relapsing, inflammatory skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions condition. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with pruritic, erythematous, thickened, scaly patches Patches Vitiligo that frequently affect flexural regions. This distribution and appearance differentiates atopic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema) from tinea versicolor and seborrheic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema). The diagnosis is clinical. Management focuses on avoiding potential triggers Triggers Hereditary Angioedema (C1 Esterase Inhibitor Deficiency), topical steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors, and immunosuppressive therapy.
• Pityriasis alba: common skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions disorder typically affecting children and adolescents. Pityriasis alba is often considered a manifestation of atopic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema). Typically, patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with erythema Erythema Redness of the skin produced by congestion of the capillaries. This condition may result from a variety of disease processes. Chalazion and scale Scale Dermatologic Examination, followed by round, hypopigmented macules and patches Patches Vitiligo, commonly occurring on the face, upper trunk, or upper limbs. The diagnosis is clinical. Pityriasis alba is considered self-limiting Self-Limiting Meningitis in Children, but it may take months to years to resolve. Topical steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors, emollients Emollients Oleaginous substances used topically to soothe, soften or protect skin or mucous membranes. They are used also as vehicles for other dermatologic agents. Pityriasis Rosea, and calcineurin Calcineurin A calcium and calmodulin-dependent serine/threonine protein phosphatase that is composed of the calcineurin a catalytic subunit and the calcineurin B regulatory subunit. Calcineurin has been shown to dephosphorylate a number of phosphoproteins including histones; myosin light chain; and the regulatory subunits of camp-dependent protein kinases. It is involved in the regulation of signal transduction and is the target of an important class of immunophilin-immunosuppressive drug complexes. Vitiligo inhibitors may be used to speed up resolution.
• Vitiligo Vitiligo Vitiligo is the most common depigmenting disorder and is caused by the destruction of melanocytes. Patients present with hypo- or depigmented macules or patches which often occur on the face, hands, knees, and/or genitalia. Vitiligo: depigmenting disorder that causes destruction of melanocytes Melanocytes Mammalian pigment cells that produce melanins, pigments found mainly in the epidermis, but also in the eyes and the hair, by a process called melanogenesis. Coloration can be altered by the number of melanocytes or the amount of pigment produced and stored in the organelles called melanosomes. The large non-mammalian melanin-containing cells are called melanophores. Skin: Structure and Functions. The etiology of vitiligo Vitiligo Vitiligo is the most common depigmenting disorder and is caused by the destruction of melanocytes. Patients present with hypo- or depigmented macules or patches which often occur on the face, hands, knees, and/or genitalia. Vitiligo is unknown, but genetic and autoimmune factors may play a role. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with hypopigmented or depigmented macules or patches Patches Vitiligo that often occur on the face, hands, knees, and/or genitalia. The diagnosis is clinical. Management can include topical corticosteroids Corticosteroids Chorioretinitis, topical calcineurin Calcineurin A calcium and calmodulin-dependent serine/threonine protein phosphatase that is composed of the calcineurin a catalytic subunit and the calcineurin B regulatory subunit. Calcineurin has been shown to dephosphorylate a number of phosphoproteins including histones; myosin light chain; and the regulatory subunits of camp-dependent protein kinases. It is involved in the regulation of signal transduction and is the target of an important class of immunophilin-immunosuppressive drug complexes. Vitiligo inhibitors, immunosuppressants Immunosuppressants Immunosuppressants are a class of drugs widely used in the management of autoimmune conditions and organ transplant rejection. The general effect is dampening of the immune response. Immunosuppressants, and phototherapy Phototherapy Treatment of disease by exposure to light, especially by variously concentrated light rays or specific wavelengths. Hyperbilirubinemia of the Newborn.
• Pityriasis rosea Pityriasis rosea Pityriasis rosea is an acute, self-limited skin disease. The etiology is not known, and it commonly occurs in young adults. Patients initially present with a single, ovoid “herald patch.” This is followed by diffuse, pruritic, scaly, oval lesions over the trunk (often in a “Christmas tree” distribution on the back) and extremities. Pityriasis Rosea: acute, self-limited skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions disorder of unknown etiology. Pityriasis rosea Pityriasis rosea Pityriasis rosea is an acute, self-limited skin disease. The etiology is not known, and it commonly occurs in young adults. Patients initially present with a single, ovoid “herald patch.” This is followed by diffuse, pruritic, scaly, oval lesions over the trunk (often in a “Christmas tree” distribution on the back) and extremities. Pityriasis Rosea presents with a single, ovoid “herald patch Patch Nonpalpable lesion > 1 cm in diameter Generalized and Localized Rashes.” This presentation is followed by diffuse, pruritic, oval plaques with fine collarette Collarette Blepharitis scale Scale Dermatologic Examination in a Christmas-tree distribution on the trunk. The diagnosis is clinical. Treatment is not required, but pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema) can be managed with emollients Emollients Oleaginous substances used topically to soothe, soften or protect skin or mucous membranes. They are used also as vehicles for other dermatologic agents. Pityriasis Rosea, topical corticosteroids Corticosteroids Chorioretinitis, and antihistamines Antihistamines Antihistamines are drugs that target histamine receptors, particularly H1 and H2 receptors. H1 antagonists are competitive and reversible inhibitors of H1 receptors. First-generation antihistamines cross the blood-brain barrier and can cause sedation. Antihistamines.
• Guttate psoriasis Psoriasis Psoriasis is a common T-cell-mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Psoriasis: variant of psoriasis Psoriasis Psoriasis is a common T-cell-mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Psoriasis, which is an immune-mediated inflammatory skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions condition. This form of psoriasis Psoriasis Psoriasis is a common T-cell-mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Psoriasis presents with small, salmon-colored papules that have a dew-drop appearance on the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions. The trunk and extremities are commonly involved. The diagnosis is clinical, and management includes topical corticosteroids Corticosteroids Chorioretinitis, calcitriol Calcitriol The physiologically active form of vitamin d. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (calcifediol). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption. Parathyroid Glands: Anatomy, and phototherapy Phototherapy Treatment of disease by exposure to light, especially by variously concentrated light rays or specific wavelengths. Hyperbilirubinemia of the Newborn. 
• Tinea corporis Tinea corporis Dermatophytes/Tinea Infections: superficial fungal infection of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions that can affect the face, trunk, and extremities. The lesions of tinea corporis Tinea corporis Dermatophytes/Tinea Infections are characterized by peripheral scaling, central clearing, and erythema Erythema Redness of the skin produced by congestion of the capillaries. This condition may result from a variety of disease processes. Chalazion. The diagnosis is usually clinical, though a KOH examination would show fungal hyphae Hyphae Microscopic threadlike filaments in fungi that are filled with a layer of protoplasm. Collectively, the hyphae make up the mycelium. Mycology. Management includes topical or oral antifungal Antifungal Azoles medications. 
• Acne vulgaris Acne vulgaris Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne Vulgaris: common disorder of the pilosebaceous units Pilosebaceous Units Hidradenitis Suppurativa in adolescents and young adults. Acne vulgaris Acne vulgaris Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne Vulgaris is caused by follicular hyperkeratinization Follicular Hyperkeratinization Acne Vulgaris, excess sebum Sebum The oily substance secreted by sebaceous glands. It is composed of keratin, fat, and cellular debris. Infectious Folliculitis production, follicular colonization Colonization Bacteriology by Cutibacterium acnes Cutibacterium acnes A bacteria isolated from normal skin, intestinal contents, wounds, blood, pus, and soft tissue abscesses. It is a common contaminant of clinical specimens, presumably from the skin of patients or attendants. Acne Vulgaris, and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation. Acne can present as open or closed comedones Closed Comedones Acne Vulgaris, papules, pustules, nodules, or cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change. The diagnosis is based on the clinical exam. Management depends on the severity, but includes skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions care techniques, topical therapies, antibiotics, and retinoids Retinoids Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Dietary vitamin A is derived from a variety of carotenoids found in plants. It is enriched in the liver, egg yolks, and the fat component of dairy products. Fat-soluble Vitamins and their Deficiencies.