Clinical History
This 45-year old patient presented with complaints of muscle weakness. Prior genetic testing detected a heterozygous variant of uncertain significance (VUS) in the GSN gene (Pathogenic variants in this gene are associated with autosomal dominant gelsolin amyloidosis). A muscle biopsy was performed to evaluated for possible myopathy.
What is the material seen within the collagen of the perimysium on the provided ultrastructural images? Congo red, Thioflavin T and immunohistochemical stain for SAP (serum amyloid P) are negative.
Answer:
The morphologic appearance is most consistent with elastin fibers (scaffold of microfibrilscomposed of fibrillin and areas of dark amorphous appearing elastin).
References:
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Kielty CM, Baldock C, Lee D, Rock MJ, Ashworth JL, Shuttleworth CA. Fibrillin: from microfibrilassembly to biomechanical function. Philos Trans R Soc Lond B Biol Sci. 2002 Feb 28;357(1418):207-17. doi: 10.1098/rst
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https://vmicro.iusm.iu.edu/hs_vm/docs/lab1_7.htmb.2001.1029. PMID: 11911778; PMCID: PMC1692929.
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