Subsarcolemmal and Cytoplasmic P62 Positivity and Rimmed Vacuoles Are Distinctive for PLIN4‐myopathy

Abstract PLIN4‐myopathy is a recently identified autosomal dominant muscular disorder caused by the coding 99 bp repeat expansion in PLIN4, presenting with distal or proximal weakness. Here, we report one family and one sporadic case of adult‐onset PLIN4‐associated limb‐girdle weakness, whose diagnoses were achieved by a comprehensive genetic analysis workup. We provided additional evidence that the combination of subsarcolemmal/cytoplasmic ubiquitin/p62 positive deposits and rimmed vacuoles could serve as a strong indicator of PLIN4‐myopathy. Moreover, we found novel myopathological features that were ultrastructural subsarcolemmal filamentous materials and membrane‐bound granulofilamentous inclusions formed by the co‐deposition of disrupted lipid droplets and p62 protein aggregates.