Erythema Nodosum MCQ — NEET PG Practice Question | NEETPGAI
Erythema Nodosum
medium
hand Dermatology
A 28-year-old woman presents with a 10-day history of bilateral, tender, warm nodules on her anterior shins. On examination, the lesions are ill-defined, erythematous, 2-3 cm in diameter, and show color changes from red to violaceous. The structure marked **A** in the diagram represents these characteristic lesions. Which of the following BEST describes the histopathological basis of the lesions marked **A**?
A. Superficial dermal vasculitis with fibrinoid necrosis of vessel walls
B. Subcutaneous abscess formation with suppurative necrosis and bacterial colonies
C. Lobular panniculitis with vasculitis and caseating granulomas
D. Septal panniculitis without vasculitis, with Miescher radial granulomas in thickened septa
Explanation
Why "Septal panniculitis without vasculitis, with Miescher radial granulomas in thickened septa" is right
Erythema nodosum (EN) is defined histopathologically as septal panniculitis WITHOUT vasculitis. The diagnostic hallmark is inflammation of the fat lobule septa with characteristic Miescher radial granulomas — small clusters of histiocytes arranged around a central cleft within the thickened septa. A deep punch or incisional biopsy is required to capture the subcutaneous fat and demonstrate these features. The lesions marked A (tender pretibial subcutaneous nodules) represent the clinical manifestation of this septal inflammatory process, which is a delayed type IV hypersensitivity reaction. (Bolognia Dermatology 5e Ch 100; Fitzpatrick 9e)
Why each distractor is wrong
Lobular panniculitis with vasculitis and caseating granulomas: This describes erythema induratum (Bazin's disease), a different panniculitis that affects the lobules (not septa), shows vasculitis, and is associated with tuberculosis. EN is septal, not lobular, and lacks vasculitis.
Superficial dermal vasculitis with fibrinoid necrosis of vessel walls: This is the histology of cutaneous polyarteritis nodosa or other vasculitic conditions, not EN. EN specifically does NOT show vasculitis.
Subcutaneous abscess formation with suppurative necrosis and bacterial colonies: This describes cellulitis or bacterial infection, not the immune-mediated panniculitis of EN. EN nodules do not ulcerate or show suppuration.
High-YieldNEET PG
EN = septal panniculitis WITHOUT vasculitis + Miescher radial granulomas = delayed hypersensitivity; erythema induratum = lobular panniculitis WITH vasculitis = TB-associated.
Bolognia Dermatology 5e Ch 100; Fitzpatrick 9e
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