Dermatology Flashcards

A 58-year-old man presents with a 2-cm violaceous nodule on the lower extremity that has been slowly enlarging over 8 months. Biopsy shows spindle cells with slit-like vascular spaces and HHV-8 positivity. His CD4 count is 420 cells/μL. Which of the following is the MOST appropriate initial management?

Answer: Initiate or optimize antiretroviral therapy alone

This patient has classic Kaposi sarcoma (KS) associated with HIV, but with a CD4 count of 420 and a single, slowly enlarging lesion without visceral involvement, this represents limited cutaneous disease. In HIV-associated KS, optimizing antiretroviral therapy (ART) alone can induce regression of limited cutaneous lesions by restoring immune function. Systemic chemotherapy (liposomal doxorubicin) is reserved for widespread cutaneous disease, rapid progression, symptomatic visceral involvement, or immune reconstitution inflammatory syndrome-associated KS. Local therapies like intralesional vinblastine or radiation are options for localized palliation but are not preferred over ART optimization as initial management in a treatment-naive or suboptimally treated patient.

A 34-year-old woman with a history of inflammatory bowel disease presents with rapidly expanding, painful ulcerations with undermined violaceous borders on her bilateral shins following minor trauma from shaving. She is afebrile, and wound cultures are negative. Histopathology shows a neutrophilic infiltrate without vasculitis. Which pathophysiologic mechanism BEST explains why surgical debridement would worsen this condition?

Answer: Pathergy leading to accelerated neutrophilic inflammation at wound sites

This patient has pyoderma gangrenosum (PG), a neutrophilic dermatosis associated with IBD. PG classically demonstrates pathergy — an exaggerated, aberrant wound-healing response in which minor trauma (including surgical debridement) triggers a disproportionate neutrophilic inflammatory cascade, causing new or worsening ulcerations at the site of the injury. This is why debridement is contraindicated in PG and can dramatically worsen the clinical picture. Koebner phenomenon (isomorphic response) refers to new lesions of a pre-existing dermatosis appearing in traumatized skin (as in psoriasis or lichen planus) and is a distinct concept. Treatment focuses on immunosuppression, not wound excision.

A 45-year-old woman presents with a 3-year history of recurrent episodes of painful, erythematous nodules on the anterior shins that resolve with bruise-like discoloration without ulceration. She has a chronic dry cough and elevated serum ACE levels. A punch biopsy of a fresh nodule reveals septal panniculitis without vasculitis. Which of the following best characterizes the underlying histologic finding and its significance?

Answer: Septal panniculitis with Miescher radial granulomas — pathognomonic for the associated systemic disease

This presentation is classic for erythema nodosum (EN) associated with sarcoidosis (elevated ACE, chronic cough). The histologic hallmark of EN is septal panniculitis (inflammation primarily in the fibrous septa between fat lobules) without vasculitis. Miescher's radial granulomas — small, nodular aggregates of histiocytes arranged radially around a central stellate cleft — are considered pathognomonic for erythema nodosum and help distinguish it from other forms of panniculitis. Their presence on biopsy, combined with the elevated ACE and pulmonary symptoms, strongly supports sarcoidosis-associated EN (Löfgren syndrome when accompanied by bilateral hilar adenopathy and arthritis). Treatment is primarily NSAIDs or potassium iodide; addressing the underlying sarcoidosis is key.

A 72-year-old man with a 25-pack-year smoking history presents with a 1.5-cm pearly papule with telangiectasias and rolled borders on his nasal ala. Dermoscopy reveals arborizing vessels and blue-gray ovoid nests. He asks about Mohs micrographic surgery versus standard wide local excision. Which factor MOST strongly justifies the use of Mohs surgery over standard excision in this specific location?

Answer: The H-zone location of the nasal ala with critical tissue conservation needs

The nasal ala lies within the H-zone (also called the mask area of the face), which includes the central face, periorbital, perinasal, perioral, and periauricular regions. These sites have high recurrence rates for basal cell carcinoma (BCC) due to complex anatomy, embryonic fusion planes that allow deeper invasion, and the critical need to conserve tissue for functional and cosmetic outcomes. Mohs surgery is the gold-standard treatment for BCCs in the H-zone regardless of size, achieving cure rates exceeding 99% while maximally preserving tissue. While tumor size >1 cm is a risk factor and blue-gray ovoid nests suggest nodular BCC (not the highest-risk subtype like morpheaform), the anatomical location on the H-zone is the primary indication here. Age alone does not independently drive the Mohs indication.

A 28-year-old woman presents with a 6-month history of episodic, symmetric, well-demarcated blanching of her fingertips followed by cyanosis and then erythema in response to cold. She also reports dysphagia, thickened skin on her fingers, and has periungual telangiectasias on exam. Her ANA is positive with anti-Scl-70 antibodies. Nailfold capillaroscopy reveals giant capillary loops and avascular areas. Which of the following statements about her vascular findings is MOST accurate?

Answer: Giant capillary loops and avascular areas indicate the 'late scleroderma' capillaroscopic pattern associated with highest risk of digital ulcers

This patient has diffuse cutaneous systemic sclerosis (dcSSc) with Raynaud's phenomenon, sclerodactyly, dysphagia, and anti-Scl-70 (anti-topoisomerase I) antibodies. Nailfold capillaroscopy is a key diagnostic and prognostic tool in connective tissue diseases. The finding of giant capillary loops with hemorrhages, reduced capillary density, and avascular areas constitutes the 'late scleroderma pattern,' which is associated with the highest risk of digital ulcers, peripheral ischemia, and systemic complications. Capillaroscopy CAN distinguish primary Raynaud's (normal findings) from secondary (structural abnormalities). Anti-Scl-70 is specifically associated with DIFFUSE cutaneous SSc and carries a HIGH risk of interstitial lung disease — not a benign limited course (which is more associated with anti-centromere antibodies). Abnormal capillaroscopy in the right clinical context strongly supports SSc.

A 52-year-old woman presents with a 2-year history of generalized pruritus, erosions, and tense bullae predominantly on her trunk and extremities. Direct immunofluorescence (DIF) of perilesional skin shows linear IgG and C3 deposition along the dermal-epidermal junction. Indirect immunofluorescence on salt-split skin shows IgG binding to the ROOF (epidermal side) of the split. Serum ELISA is positive for BP180 and BP230 antibodies. She fails to respond adequately to high-dose topical clobetasol. What is the MOST appropriate next-line systemic therapy based on current evidence?

Answer: Oral prednisone 0.5 mg/kg/day combined with doxycycline 200 mg/day

This patient has bullous pemphigoid (BP), confirmed by tense bullae, linear IgG/C3 at the DEJ on DIF, roof-binding on salt-split skin (confirming antibodies target hemidesmosomal proteins above the lamina densa), and positive BP180/BP230 ELISA. When high-potency topical steroids fail or are insufficient, the current evidence-based first-line systemic option for BP is oral prednisone combined with doxycycline. Multiple randomized trials (including the BLISTER trial) have shown that doxycycline 200 mg/day (as monotherapy or combined with low-dose prednisolone) achieves disease control comparable to systemic steroids alone but with a superior safety profile — particularly important given BP's typical patient population (elderly with comorbidities). Rituximab and IVIG are reserved for refractory or severe cases. Dupilumab (anti-IL-4Rα) has emerging evidence for BP but is not yet established as the second-line standard of care.