A 45-year-old man with known HIV infection comes to the emergency department due to a rash that began on his hands 4-5 weeks ago but then spread to involve his upper arms, shoulders, and ears. He has no fever, trauma, recent travel, or insect bites. He lives in a shelter and has poor medical follow-up. The patient was treated in the past for Candida esophagitis and Pneumocystis jirovecii pneumonia. His CD4⁺ cell count 6 months ago was 50/µL. His temperature is 36.7 C (98 F) , blood pressure is 126/80 mm Hg, and pulse is 80/min. Photographs of the patient's skin examination are shown below.

Which of the following is the most likely diagnosis?

Question

A 45-year-old man with known HIV infection comes to the emergency department due to a rash that began on his hands 4-5 weeks ago but then spread to involve his upper arms, shoulders, and ears. He has no fever, trauma, recent travel, or insect bites. He lives in a shelter and has poor medical follow-up. The patient was treated in the past for Candida esophagitis and Pneumocystis jirovecii pneumonia. His CD4⁺ cell count 6 months ago was 50/µL. His temperature is 36.7 C (98 F) , blood pressure is 126/80 mm Hg, and pulse is 80/min. Photographs of the patient's skin examination are shown below.

Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Simple scabies is due to the Sarcoptes scabiei mite, which burrows into the skin and spreads through person-to-person contact. It usually presents with an intensely pruritic rash in the flexor surfaces of the wrist, lateral surfaces of the fingers, and the finger webs. It can also involve other parts of the body but less commonly affects the back and head (except in children). Examination usually shows excoriations with small, crusted, red papules. scabies In contrast, crusted scabies is an overwhelming infestation with thousands (compared to <50 in simple scabies) of scabies mites that is more common in elderly or immunocompromised (eg, HIV) patients. Crusted scabies causes little or no itching, and presents insidiously with poorly defined erythematous patches that progress to prominent scales, crusting, and malodorous fissures. Affected areas can include the palms, extensor surfaces of the hands and elbows, scalp, ears, feet, and toes. Patients may develop secondary infections of the skin. Diagnosis is confirmed by skin scraping or dermatoscopy showing the mites and eggs. Simple scabies can be treated with topical permethrin, but topical agents alone are not as effective for crusted scabies due to the significant mite burden and the extensive crusting that diminishes penetration of the drug. Treatment requires oral ivermectin along with topical application of a keratolytic agent (eg, 20% urea ointment) and permethrin. (Choice B) Eczema in adults usually presents as erythematous plaques with thickened skin, lichenification (increased skin markings), and excoriation. The rash is usually pruritic and commonly involves the neck, antecubital fossa, popliteal fossa, face, wrists, and forearms. Eczema (Choice C) Psoriasis presents with well-defined erythematous, scaly plaques involving the scalp, extensor surfaces of the elbows, knees, external ear, and back. Psoriasis can be more severe in HIV patients with involvement of the palms, feet, nails, and sometimes widespread erythroderma. However, this patient's involvement of the hands, shoulders, and face makes psoriasis less likely. Psoriasis (Choice D) Seborrheic dermatitis usually presents as erythematous patches with a fine greasy scale on the scalp, eyebrows, central face, and trunk. Patients with HIV can have more severe, widespread seborrheic dermatitis, but this patient's crusting and fissuring is more consistent with crusted scabies. widespread seborrheic dermatitis (Choice E) Tinea corporis is a dermatophyte infection that causes a ring of erythema and scaling as opposed to the diffuse crusted lesions seen in this patient. Tinea corporis Educational objective: Crusted scabies is an overwhelming infestation with thousands (compared to <50 in simple scabies) of scabies mites. It is more common in the elderly and immunocompromised (eg, HIV) and presents with erythematous patches that progress to prominent scales, crusting, and malodorous fissures. Itching is mild or absent. Treatment requires oral ivermectin with a topical keratolytic agent (eg, 20% urea ointment) and permethrin. __________ References: Crusted scabies. (http://www.ncbi.nlm.nih.gov/pubmed/19584457)

A 45-Year-Old Man with Known HIV Infection Comes to the Emergency