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Washington University Experience | MUSCLE | Myopathies with Mitochondrial Pathology | 18A0 Case 18 History
Case 18 History ---- The patient is a 72-year-old man with over 5 years of a progressive myopathy causing weakness and a stooped posture. NM Division workup EMG/NCS studies showed electrodiagnostic evidence of a mild, chronic, patchy, non-irritable myopathy, a conclusion based on normal to reduced insertional activity and mild myopathic motor unit potential changes with recruitment patterns of varying severity in muscles of the left upper and lower limbs, with the most severe changes evident in the two axial muscles sampled. Reduced insertional activity in multiple muscles suggests a chronic process with replacement of muscle fibers by connective tissue and/or fat. Operative procedure: Right paraspinal, right trapezius, and right deltoid muscle biopsies. Serum testing showed an IgG kappa MCP and borderline positive Mi-2β antibodies. Genetic testing showed a pathogenic mutation in DNMT3B with a permissive 4q35 allele and hypomethylation (i.e., a genotype compatible with FSHD4). There is clinical concern for a concurrent acquired myopathy, including SLONM. Both paraspinal and axial (trapezius and deltoid) muscles were biopsied and analyzed.
