An 18-month-old infant presents with a diffuse rash that has worsened over the past 24 hours. His mother reports that he has been lethargic with a decreased appetite. The child is otherwise healthy, but did have symptoms consistent with an upper respiratory infection a few weeks prior to the onset of the rash. Physical examination reveals an afebrile infant with the following dermatologic finding shown below.
Which of the following is the most common cause of this condition?
Herpes simplex virus. The patient in this question is presenting with pink-red papules and plaques with a pale central regions. The skin lesions have a “target” appearance, a classic description for erythema multiforme (EM). EM is a skin condition whose cause remains unclear but likely is secondary to immune complex deposition in superficial microvasculature of the skin. EM usually follows infection or drug exposure. The most common cause of EM is herpes simplex virus (HSV). (A, C, D) Drug reactions (sulfa drugs, phenytoin, β-lactam antibiotics), Mycoplasma pneumoniae, and non-Hodgkin lymphoma are also causes of EM, but not as common as HSV infection.
A 77-year-old man presents with a rough bump on his left ear. It is sometimes pruritic, but otherwise is not bothersome. He endorses significant sun exposure in his youth and admits to rarely using sunscreen when he is outdoors. On physical examination, the following is seen below.
For which of the following conditions is this skin condition a precursor?
Squamous cell carcinoma. The patient in this question is presenting with an actinic keratosis, a small and rough papule (erythematous, brownish, or skin-colored) whose risk of carcinoma depends on the degree of epithelial dysplasia. Actinic keratoses are precursors for squamous cell carcinoma, a locally invasive skin cancer that rarely metastasizes. Risk increases with excessive sun exposure and arsenic exposure. (A) Although melanoma is not associated with actinic keratoses, melanoma is also associated with sunlight exposure. Dysplastic nevi are precursors to melanoma. (B) Basal cell carcinomas are not formed from actinic keratoses. Similar to squamous cell carcinoma, basal cell carcinoma is locally invasive and rarely metastasizes. (D) Cutaneous T-cell lymphoma is not associated with actinic keratoses.
A 41-year-old woman presents with tender and enlarged lumps on her shins. She also endorses weakness, subjective fevers, and arthralgia. On physical examination, the following is seen below.
Which of the following is NOT associated with this dermatologic condition?
Diabetes mellitus type 2. The patient in this question is presenting with erythema nodosum, inflammatory lesions of subcutaneous fat that are usually located on the shins. The nodules are usually tender and typically resolve in 1 to 2 months. (A, B, C) Although the cause of erythema nodosum is commonly unknown, it has been associated with sarcoidosis, inflammatory bowel disease, and streptococcal infection (especially in children). It has also been associated with coccidioidomycosis, histoplasmosis, TB, and leprosy. It is not associated with diabetes.
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