Histopathological examination of a skin biopsy from a patient with dermatomyositis shows perifascicular atrophy in the muscle biopsy. On the skin biopsy of Gottron's papules, which finding distinguishes dermatomyositis from systemic lupus erythematosus?
- A Mucin deposition in the dermis is exclusive to dermatomyositis
- B Dermatomyositis shows lichenoid tissue reaction; SLE shows vacuolar change only
- C SLE shows neutrophilic infiltrate; dermatomyositis shows eosinophilic infiltrate
- D Both show identical interface dermatitis; dermatomyositis additionally shows dermal mucin ✓
Explanation
Both dermatomyositis (DM) and lupus erythematosus (LE) show interface dermatitis with vacuolar degeneration of the basal layer, dyskeratotic keratinocytes, and perivascular lymphocytic infiltrate — making them histopathologically similar. The key distinguishing feature of DM is the presence of increased dermal mucin (glycosaminoglycans) between collagen bundles, which is characteristically prominent in DM skin lesions. SLE can also have some mucin but it is more pronounced in DM. Additionally, DM may show thickened basement membrane on PAS staining. DIF is unhelpful in distinguishing them, as DM rarely shows immunodeposits unlike LE's positive lupus band.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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