A 45-year-old woman comes to the office with a 10-day history of a pruritic rash. The rash initially started on her hands and quickly spread to her fingers, wrists, and elbows. The itching is particularly pronounced at night. The patient works as a flight attendant and recently returned from an international trip, during which she stayed in a hotel for 3 days. Her roommate also developed similar symptoms a week after the patient did. The patient has no other medical conditions and takes no medications. She has one sexual partner and uses condoms for contraception. Her mother has a history of atopic dermatitis. Vital signs are normal. Skin examination shows small erythematous papules on the palms with scattered vesicles and pustules on the finger webs, palms, and wrist creases as shown below. There are numerous excoriations on the wrists and elbows. The remainder of the examination is within normal limits. Which of the following is the most likely diagnosis?

Question

A 45-year-old woman comes to the office with a 10-day history of a pruritic rash.  The rash initially started on her hands and quickly spread to her fingers, wrists, and elbows.  The itching is particularly pronounced at night.  The patient works as a flight attendant and recently returned from an international trip, during which she stayed in a hotel for 3 days.  Her roommate also developed similar symptoms a week after the patient did.  The patient has no other medical conditions and takes no medications.  She has one sexual partner and uses condoms for contraception.  Her mother has a history of atopic dermatitis.  Vital signs are normal.  Skin examination shows small erythematous papules on the palms with scattered vesicles and pustules on the finger webs, palms, and wrist creases as shown below.  There are numerous excoriations on the wrists and elbows.  The remainder of the examination is within normal limits.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec25c8_d389_e7f0_bc81_ab61643470bb_MD0003_00 Scabies is due to infestation by Sarcoptes scabiei mites, which spread through person-to-person contact. The mites burrow into the skin, leading to a delayed type IV hypersensitivity reaction to the mite, feces, and eggs. Scabies presents with an intensely pruritic rash with small, crusted, red papules and linear burrows. Patients can also develop vesicles, pustules, and wheals with extensive excoriations. The most common locations include the flexor surface of the wrist, lateral surfaces of the fingers, and the finger webs. Scabies can affect exposed and unexposed skin. Diagnosis is confirmed by light microscopy of skin scrapings revealing mites, ova, and feces. Topical permethrin or oral ivermectin can eliminate the infestation. Bedding and clothing should be cleaned or placed in a plastic bag for >3 days as mites can live away from human skin for only 2-3 days. > (Choice A) Bed bugs hide in old furniture and in the seams and folds of mattresses, come out at night to feed on exposed skin, and then return to their hiding spot. However, bed bug bites most often cause small, punctate lesions with surrounding erythema, classically in linear tracks or clusters ("breakfast, lunch, and dinner" bites). Bites on the palms and soles are uncommon due to the thickness of the skin. Intense pruritus that is worse at night, pustules, finger web involvement, and excoriations (due to mites digging burrows) are all more suggestive of scabies. Bed bugs (Choice B) Bullous pemphigoid is an autoimmune disease most commonly affecting individuals age >60. Patients have a prodrome of eczematous or urticarial lesions and subsequently develop tense bullae and plaques affecting the flexural areas, groin, or axilla. Bullous pemphigoid (Choice C) Eczema usually presents as pruritic, erythematous plaques with thickened skin, lichenification (increased skin markings), and fibrotic papules with excoriation. The rash commonly involves the neck, antecubital fossa, popliteal fossa, face, wrists, and forearms. Eczema (Choice E) Seborrheic dermatitis presents as erythematous patches with fine, greasy scales on the scalp, eyebrows, central face, and trunk. Seborrheic dermatitis (Choice F) Secondary syphilis is characterized by fever, lymphadenopathy, and a nonpruritic, maculopapular rash with variable distribution involving the trunk and extremities. Secondary syphilis (Choice G) Urticaria presents as evanescent wheals or hives with intense itching. Most incidents resolve in <24 hours. Urticaria Educational objective: Scabies is due to infestation by Sarcoptes scabiei mites and causes a pruritic rash in the flexor surfaces of the wrist, lateral surfaces of the fingers, and the finger webs. Patients usually have excoriations and crusted, red papules in the affected areas. Diagnosis is confirmed by light microscopy of skin scrapings. Topical permethrin or oral ivermectin is the preferred treatment in adults. References: Pediculosis and scabies: treatment update. (http://www.ncbi.nlm.nih.gov/pubmed/23062045) Scabies. (http://www.ncbi.nlm.nih.gov/pubmed/19580575)

A 45-Year-Old Woman Comes to the Office with a 10-Day