A 36-year-old man comes to the office to discuss a skin rash on his shoulders and upper chest. The patient first noticed the rash 2 months ago while vacationing at a beach resort. The rash has worsened progressively and is associated with mild pruritus, but he has no other associated symptoms. The patient is a road construction worker, and often works in hot, humid areas. Past medical history is notable for seasonal allergies and childhood asthma. He does not use tobacco or alcohol. Skin examination findings are shown in the image below. Which of the following is the most likely cause of this patient's condition?

Question

A 36-year-old man comes to the office to discuss a skin rash on his shoulders and upper chest.  The patient first noticed the rash 2 months ago while vacationing at a beach resort.  The rash has worsened progressively and is associated with mild pruritus, but he has no other associated symptoms.  The patient is a road construction worker, and often works in hot, humid areas.  Past medical history is notable for seasonal allergies and childhood asthma.  He does not use tobacco or alcohol.  Skin examination findings are shown in the image below.  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_37ef_8d4b_9249_81433e78a6d2_MD0001_00 Pityriasis versicolor (also called tinea versicolor) is characterized by hypopigmented, hyperpigmented, or erythematous macules or patches on the upper body. It is caused by Malassezia species yeasts, and the infection is confined to the stratum corneum of the skin. It is common in areas with hot and humid climates and is often most visible after extensive sun exposure due to tanning of the adjacent skin. Most cases of pityriasis versicolor occur in healthy individuals with no underlying immunologic deficiencies. The diagnosis of pityriasis versicolor is made by potassium hydroxide (KOH) preparation of skin scrapings. Malassezia forms spores and hyphae, producing the characteristic "spaghetti and meatballs" appearance on light microscopy. The hyphae have a short, "cigar-butt" appearance. This condition is treated with topical antifungal agents or selenium-containing shampoo. (Choices A and C) Blastomycosis is characterized by progressive pulmonary infection. Skin involvement is uncommon but can manifest as papular or pustular lesions in exposed areas. Histoplasmosis also most commonly causes pulmonary disease, though it may become disseminated in immunodeficient patients. (Choice B) Intertrigo is characterized by well-defined erythematous plaques with satellite vesicles or pustules in warm, moist skin areas (eg, axillae, groin, skin folds). The infection is usually due to Candida species, and it is most common following antibiotic use or in immunocompromised states (eg, uncontrolled diabetes). (Choice E) Microsporum species are a frequent cause of tinea capitis and tinea corporis. (Choice F) Rhizopus is a major cause of mucormycosis, which is characterized by invasive, necrotic upper and lower respiratory infections in immunocompromised patients. (Choice G) Sporothrix molds are found in decaying horticultural matter and are acquired through breaks in the skin. They cause nodular and ulcerating subcutaneous lesions. Educational objective: Pityriasis versicolor (tinea versicolor) is a superficial skin infection caused by Malassezia species. It causes erythematous, hyper- or hypopigmented macules and patches. Malassezia forms spores and hyphae, producing the characteristic "spaghetti and meatballs" appearance on KOH preparation light microscopy. __________ References: Microreview of pityriasis versicolor and Malassezia species. (http://www.ncbi.nlm.nih.gov/pubmed/17146580)

A 36-Year-Old Man Comes to the Office to Discuss a Skin