Dermatopathology, Pathology, USMLE Step 1 - Full Vignette with Extended Explanations скачать в хорошем качестве

Dermatopathology, Pathology, USMLE Step 1 - Full Vignette with Extended Explanations

A 32-year-old woman presents with four months of painful oral erosions, conjunctival redness, polymorphous trunk lesions, and weight loss. Imaging reveals an isolated anterior mediastinal mass, while immunofluorescence studies show combined intercellular and basement membrane staining. Given her mucocutaneous findings and challenging serology, which additional diagnostic test can help distinguish between autoimmune blistering disorders in this complex clinical scenario? VIDEO INFO Category: Dermatopathology, Pathology, USMLE Step 1 Difficulty: Hard - Advanced level - Challenges experienced practitioners Question Type: Differential Testing Case Type: Rare Presentation Explore more ways to learn on this and other topics by going to https://endlessmedical.academy/auth?h... QUESTION A 32-year-old woman with hypoparathyroidism and Wolff-Parkinson-White syndrome presents with 4 months of recalcitrant, exquisitely painful erosive stomatitis involving the buccal mucosa, soft palate, and vermilion lips, associated with conjunctival injection and a polymorphous eruption of flaccid vesicles, erosions, and lichenoid papules on the trunk. She reports odynophagia, weight loss of 3.6 kg, and intermittent nonproductive cough.... OPTIONS A. Indirect immunofluorescence using patient serum on rat bladder (transitional epithelium) to detect anti-plakin reactivity characteristic of paraneoplastic pemphigus. B. Repeat ELISA quantification of anti-desmoglein 1 and anti-desmoglein 3 antibodies with a different commercial platform to improve pemphigus vulgaris detection. C. In situ hybridization for EBV in the mediastinal lesion to evaluate for an EBV-driven lymphoproliferative process as the primary discriminator between pemphigus subtypes. D. Western blot limited to desmoglein antigens performed on human epidermal extracts to enhance sensitivity for pemphigus vulgaris versus paraneoplastic pemphigus. CORRECT ANSWER A. Indirect immunofluorescence using patient serum on rat bladder (transitional epithelium) to detect anti-plakin reactivity characteristic of paraneoplastic pemphigus. EXPLANATION The decisive test when desmoglein-restricted assays are unrevealing and both intercellular and basement membrane zone staining are present on mucosal direct immunofluorescence is indirect immunofluorescence using patient serum on rat bladder transitional epithelium. Transitional epithelium expresses plakin-family antigens (envoplakin, periplakin, desmoplakin I/II, plectin, BP230) highly; binding yields the characteristic cytoplasmic cell-surface pattern that identifies anti-plakin reactivity, which is a hallmark of paraneoplastic pemphigus. In the clinical setting of severe recalcitrant stomatitis, polymorphous eruption, and an isolated FDG-avid mediastinal mass, positive rat bladder indirect immunofluorescence strongly supports paraneoplastic pemphigus and separates it from classic pemphigus vulgaris. The proposed alternatives will not resolve this specific differential. Repeating desmoglein ELISA on a different platform does not evaluate plakin reactivity and can be negative in paraneoplastic pemphigus or even low-positive in pemphigus variants; it does not distinguish the two entities when prior Dsg assays are unrevealing. In situ hybridization for EBV within the mass may help characterize certain lymphoproliferative disorders but is not a discriminator between pemphigus vulgaris and paraneoplastic pemphigus.... Further reading: Links to sources are provided for optional further reading only. The questions and explanations are independently authored and do not reproduce or adapt any specific third-party text or content. --------------------------------------------------- Our cases and questions come from the https://EndlessMedical.Academy quiz engine - multi-model platform. Each question and explanation is forged by consensus between multiple top AI models (i.e. Open AI GPT, Claude, Grok, etc.), with automated web searches for the latest research and verified references. Calculations (e.g. eGFR, dosages) are checked via code execution to eliminate errors, and all references are reviewed by several AIs to minimize hallucinations. Important note: This material is entirely AI-generated and has not been verified by human experts; despite stringent consensus checks, perfect accuracy cannot be guaranteed. Exercise caution - always corroborate the content with trusted references or qualified professionals, and never apply information from this content to patient care or clinical decisions without independent verification. Clinicians already rely on AI and online tools - myself included - so treat this content as an additional focused aid, not a replacement for proper medical education. Visit https://endlessmedical.academy for more AI-supported resources and cases. This material can not be treated as medical advice. May contain errors. ---------------------------------------------------