ABD - American Board of Dermatology Cutaneous Infectious Diseases Questions and Answers 1 — 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?
- Coccidioidomycosis
- Blastomycosis (Correct answer)
- Sporotrichosis
- Histoplasmosis
Correct answer: Blastomycosis
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:
- Erysipeloid spread
- Tuberculoid spread
- Sporotrichoid spread (Correct answer)
- Herpetiform spread
Correct answer: Sporotrichoid spread
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?
- Desmoglein 3
- Collagen VII
- Keratin 14
- Desmoglein 1 (Correct answer)
Correct answer: Desmoglein 1
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?
- Presence of multiple excoriations
- Identification of the mite, its eggs, or its feces (scybala) (Correct answer)
- Peripheral eosinophilia on a complete blood count
- A positive burrow ink test showing a zig-zag line
Correct answer: Identification of the mite, its eggs, or its feces (scybala)
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?
- Topical acyclovir cream
- Oral valacyclovir
- Intravenous acyclovir (Correct answer)
- Prednisone taper
Correct answer: Intravenous acyclovir
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.
Question 6: An 8-year-old child returns from a camping trip in North Carolina and develops an abrupt onset of high fever, severe headache, and myalgias. Four days later, a maculopapular rash appears, starting on the wrists and ankles and then spreading to the trunk, palms, and soles. The rash gradually becomes petechial. This classic presentation is most characteristic of which infectious disease?
- Lyme disease
- Ehrlichiosis
- Rocky Mountain Spotted Fever (Correct answer)
- Babesiosis
Correct answer: Rocky Mountain Spotted Fever
The classic triad of fever, headache, and rash, especially a rash that begins on the extremities (wrists and ankles) and spreads centripetally to include the palms and soles, is highly characteristic of Rocky Mountain Spotted Fever (RMSF). RMSF is caused by Rickettsia rickettsii and transmitted by ticks, and it is endemic in North Carolina.
ABD - American Board of Dermatology Cutaneous Infectious Diseases Questions and Answers 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?