ABD - American Board of Dermatology Cutaneous Infectious Diseases Questions and Answers

Question 1

A 52-year-old man from rural Wisconsin presents with a one-month history of non-healing, verrucous plaques on his face and chest. He also reports a persistent cough and low-grade fever. A skin biopsy reveals pseudoepitheliomatous hyperplasia with dermal microabscesses. Within the abscesses, large, thick-walled yeasts with single, broad-based buds are identified. Which of the following is the most likely diagnosis?

Accepted Answer

Blastomycosis

Answer

The clinical presentation of verrucous skin lesions and pulmonary symptoms, combined with the geographic location (Wisconsin, an endemic area), strongly suggests a deep fungal infection. The key histopathologic finding of large yeasts with single, broad-based buds is pathognomonic for Blastomycosis, caused by Blastomyces dermatitidis.

Question 2

An aquarium enthusiast develops a papule on his right index finger two weeks after sustaining a small cut while cleaning his fish tank. Over the next month, several more erythematous nodules appear in a linear fashion ascending up his forearm. This specific clinical pattern is best described as:

Accepted Answer

Sporotrichoid spread

Answer

The patient's history of a fish tank injury followed by the development of nodules ascending along the lymphatic drainage is a classic presentation for Mycobacterium marinum infection, also known as 'fish tank granuloma'. This linear arrangement of nodules along lymphatic channels is termed a sporotrichoid pattern or spread, named after its resemblance to the presentation of sporotrichosis.

Question 3

A 3-year-old child is hospitalized with a diffuse, tender erythema that began around the mouth and flexures, followed by the formation of large, flaccid bullae and a positive Nikolsky sign. The mucous membranes are spared. The pathogenesis of this condition involves a bacterial exotoxin that specifically cleaves which of the following structural proteins?

Accepted Answer

Desmoglein 1

Answer

The clinical picture is classic for Staphylococcal Scalded Skin Syndrome (SSSS). This condition is caused by exfoliative toxins (ETA and ETB) produced by Staphylococcus aureus. These toxins act as serine proteases that specifically target and cleave desmoglein 1, a desmosomal adhesion molecule, leading to intraepidermal splitting at the granular layer. The sparing of mucous membranes is due to the presence of desmoglein 3 in those tissues, which compensates for the loss of desmoglein 1 function.

Question 4

Which of the following findings on a mineral oil skin scraping is considered definitive for the diagnosis of scabies?

Accepted Answer

Identification of the mite, its eggs, or its feces (scybala)

Answer

While clinical signs like burrows and excoriations are highly suggestive, the definitive diagnosis of scabies is made by the direct visualization of the causative agent, Sarcoptes scabiei, or its products. A mineral oil preparation of a skin scraping from a burrow allows for microscopic identification of the adult mite, eggs, or fecal pellets (scybala), confirming the infestation.

Question 5

A 55-year-old immunocompromised man with a recent organ transplant is admitted with a severe, painful, vesiculobullous eruption in a C6 dermatomal distribution. The lesions are hemorrhagic and beginning to show signs of necrosis. What is the most appropriate initial therapeutic intervention?

Accepted Answer

Intravenous acyclovir

Answer

This patient presents with severe, complicated herpes zoster (shingles) in the setting of immunosuppression. The hemorrhagic and necrotic features indicate a high risk for dissemination and other complications. In immunocompromised patients or those with severe/disseminated zoster, intravenous acyclovir is the standard of care and the most appropriate initial treatment to ensure adequate drug levels and prevent systemic complications.

American Board of Dermatology (ABD) Practice Test

American Board of Dermatology (ABD) Practice Test

ABD - American Board of Dermatology Cutaneous Infectious Diseases Questions and Answers