Which of the following is the most specific indirect immunofluorescence finding that distinguishes paraneoplastic pemphigus from pemphigus vulgaris?

• A Positive indirect immunofluorescence using monkey esophagus substrate
• B Positive indirect immunofluorescence using salt-split normal human skin
• C Positive indirect immunofluorescence using guinea pig esophagus
• D Positive indirect immunofluorescence using rat bladder transitional epithelium ✓

Explanation

Paraneoplastic pemphigus produces autoantibodies against plakins (desmoplakin, envoplakin, periplakin). These are detected as positive indirect immunofluorescence on rat bladder transitional epithelium, which is rich in plakins. This substrate is negative in pemphigus vulgaris. Monkey esophagus is positive in both. Salt-split skin shows intercellular staining in pemphigus and is not the discriminating test.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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