Dermatology Flashcards

A 45-year-old woman with butterfly-shaped facial erythema sparing the nasolabial folds, discoid lesions on the scalp, and photosensitivity is found to have oral ulcers and positive ANA. Which of the following skin findings would be MOST characteristic of her underlying diagnosis?

Answer: Malar rash sparing the nasolabial folds

The malar (butterfly) rash of SLE characteristically spares the nasolabial folds, distinguishing it from rosacea. Psoriasiform plaques are seen in psoriasis. Gottron's papules are pathognomonic for dermatomyositis. Target lesions suggest erythema multiforme.

A 55-year-old man who recently started allopurinol presents with widespread erythema, skin sloughing affecting >30% of body surface area, mucosal involvement, and fever. Skin biopsy shows full-thickness epidermal necrosis. What is this condition?

Answer: Toxic epidermal necrolysis (TEN)

TEN is defined by epidermal detachment affecting >30% BSA with full-thickness epidermal necrosis on biopsy, commonly drug-induced (allopurinol, sulfonamides, anticonvulsants). SJS involves <10% BSA detachment. SSSS affects mainly children and involves superficial epidermal cleavage from staph exotoxin. Pemphigus vulgaris presents with flaccid blisters from autoantibodies, not drug-induced.

A 30-year-old woman presents with a pruritic, well-demarcated, silvery-scaled plaques on the elbows, knees, and scalp. She also reports nail pitting. Which of the following systemic associations should be screened for in this patient?

Answer: Psoriatic arthritis

Psoriasis is strongly associated with psoriatic arthritis, which occurs in approximately 20–30% of psoriasis patients. Internists should screen for joint symptoms, enthesitis, and dactylitis. While psoriasis has some immune associations, psoriatic arthritis is the most clinically relevant and directly linked systemic comorbidity to screen for.

A 62-year-old man presents with a 3-week history of grouped vesicles on an erythematous base in a dermatomal distribution along the left T5–T6 dermatome, with significant burning pain. He is immunocompetent. Which of the following is the most appropriate management?

Answer: Valacyclovir 1000 mg three times daily for 7 days, started within 72 hours of rash onset

Oral valacyclovir (or famciclovir) is first-line for herpes zoster in adults, particularly to reduce duration, severity, and risk of postherpetic neuralgia. It must be started within 72 hours of rash onset for maximum benefit. Topical acyclovir is inadequate. Steroids alone without antivirals are not recommended. Treatment is always recommended in adults due to postherpetic neuralgia risk.

A 50-year-old man with a history of heavy alcohol use presents with multiple firm, yellowish-orange plaques on his Achilles tendons and extensor tendons of the hands. Fasting lipid panel shows total cholesterol 380 mg/dL, LDL 290 mg/dL, triglycerides 140 mg/dL, HDL 42 mg/dL. What is the most likely underlying diagnosis?

Answer: Familial hypercholesterolemia

Tendinous xanthomas (especially on the Achilles and extensor tendons) are pathognomonic for familial hypercholesterolemia (FH), caused by LDL receptor mutations leading to very high LDL. Hypertriglyceridemia causes eruptive xanthomas and pancreatitis, not tendinous xanthomas. Type 3 hyperlipidemia causes palmar xanthomas. Alcohol elevates triglycerides primarily.

A 38-year-old woman presents with a blistering rash. On examination, flaccid bullae arise on normal-appearing skin, rupture easily leaving erosions, and the Nikolsky sign is positive (lateral pressure causes skin to shear). Direct immunofluorescence shows intercellular IgG deposition in a 'fishnet' pattern in the epidermis. What is the diagnosis?

Answer: Pemphigus vulgaris

Pemphigus vulgaris is an autoimmune blistering disease characterized by flaccid bullae, positive Nikolsky sign, mucosal involvement, and intercellular IgG deposition (anti-desmoglein antibodies) in a fishnet/reticular pattern on DIF. Bullous pemphigoid has tense bullae, negative Nikolsky, and linear IgG at the dermal-epidermal junction. Dermatitis herpetiformis shows IgA deposits in papillary dermis.