Dermatology · Papulosquamous Disorders
The facts most likely to be tested
Seborrheic dermatitis is an inflammatory condition strongly associated with the overgrowth of the commensal yeast Malassezia furfur.
Clinical presentation typically involves erythematous plaques with greasy, yellow-colored scales in areas of high sebaceous gland activity.
The classic distribution includes the scalp (dandruff), nasolabial folds, eyebrows, eyelids, and the presternal area.
Patients with Parkinson disease or HIV/AIDS have a significantly increased incidence and severity of seborrheic dermatitis.
First-line treatment for scalp involvement consists of topical antifungal shampoos containing ketoconazole, selenium sulfide, or zinc pyrithione.
Facial or intertriginous involvement is managed with low-potency topical corticosteroids or topical calcineurin inhibitors for short-term control.
Infantile seborrheic dermatitis, known as cradle cap, is a self-limiting condition typically managed with emollients and gentle removal of scales.
Vignette unlocked
A 58-year-old male with a history of Parkinson disease presents to the clinic complaining of persistent itching and flaking on his face. Physical examination reveals erythematous patches with greasy, yellow-colored scales located in the nasolabial folds and along the eyebrows. The patient reports that the condition worsens during periods of stress. He has no history of recent medication changes or systemic symptoms.
What is the most likely diagnosis?
Seborrheic dermatitis
The patient's presentation of greasy, yellow scales in seborrheic areas (nasolabial folds, eyebrows) combined with his history of Parkinson disease is classic for seborrheic dermatitis, as described in the bets.
Full handout
High yield triage
Etiology / Epidemiology
Common inflammatory condition linked to Malassezia yeast overgrowth in sebum-rich areas.
Clinical Manifestations
Erythematous plaques with greasy yellow scales; cradle cap in infants.
Diagnosis
Clinical diagnosis; biopsy is rarely indicated unless refractory.
Treatment
Ketoconazole shampoo is first-line; use topical steroids for flares.
Prognosis
Chronic, relapsing course; no long-term sequelae.
Full handout
Epidemiology & Etiology
Affects all ages, with peaks in infancy and adulthood. Associated with Parkinson disease and HIV/AIDS due to altered immune response or sebum production. Triggered by stress, cold weather, and fatigue.
Pertinent Anatomy
Predominantly affects areas with high density of sebaceous glands. Key sites include the scalp, face (nasolabial folds, eyebrows), and presternal chest.
Pathophysiology
Inflammatory reaction to the commensal yeast Malassezia furfur. The yeast metabolizes sebum, releasing free fatty acids that irritate the skin. Host immune response to these metabolites drives the characteristic scaling and erythema.
Clinical Manifestations
Presents as erythematous patches with greasy, yellow-white scales. In infants, it is known as cradle cap. In adults, it often involves the scalp (dandruff) and central face. Red flags include generalized erythroderma or failure to respond to standard therapy, which may suggest underlying immunodeficiency.
Diagnosis
Primarily a clinical diagnosis based on morphology and distribution. Biopsy is the gold standard if the diagnosis is uncertain, typically showing spongiosis and parakeratosis. No specific laboratory values are diagnostic.
Treatment
First-line therapy is Ketoconazole shampoo or cream to reduce yeast load. For facial involvement, use low-potency topical steroids (e.g., hydrocortisone) for short durations. Avoid long-term use of high-potency steroids on the face to prevent skin atrophy.
Prognosis
Condition is chronic and relapsing. No long-term complications exist, though patients require intermittent maintenance therapy. Remission is common in infants by 6-12 months of age.
Differential Diagnosis
Psoriasis: silvery scales and extensor surface involvement
Atopic dermatitis: intense pruritus and flexural distribution
Tinea capitis: hair loss and fungal hyphae on KOH prep
Rosacea: telangiectasias and absence of greasy scaling
Langerhans cell histiocytosis: persistent, refractory seborrheic-like rash in infants