Presentation
Previously fit male presenting with unintentional weight loss, weakness, and dysphagia.
Patient Data
Diffuse thickening, with fascial layers surrounding the bilateral thigh muscles showing as hyperintense on T2. Bilateral high STIR signal within the vastus lateralis (right greater than left). Incidental 29mm lipoma left posterior thigh.
Case Discussion
Histology Report (biopsy from right vastus lateralis)
Microscopic description: The sections of skeletal muscle show connective tissues within which there is an infiltrate of histiocytes and a perifascicular pattern of atrophy and degeneration of muscle fibers, seen in association with an upregulation of alkaline phosphatase in the perimysial tissues. There is minimal lymphocytic infiltrate. There is no increase in lipid and glycogen. The perifascicular fibers show abnormal myofibrillary matrix. Normal phosphorylase and AMP deaminase and normal cytochrome oxidase. Muscle appears to be focally type I dominant, with atrophy of mostly type II fibers.
Diagnostic opinion: Skeletal muscle from right vastus lateralis, showing features in keeping with an immune-mediated perimysial pathology of some weeks duration. Changes are in keeping with an RNA-synthetase syndrome/anti PL-7.
EMG/NCS Report
There is a length-dependent sensorimotor axonal neuropathy. There is a superimposed severe myopathy affecting proximal right upper and lower limb muscles sampled. With the exception of the right tibialis anterior, the remainder of the muscles sampled have no features of myonecrosis (i.e. this is a non-irritative myopathy).
CT Chest completed at an external hospital prior to admission illustrated mild non-specific ground-glass opacities.
Interestingly, the patient did not present with the cutaneous features that may be expected with dermatomyositis, likely due to the nature of the anti-PL-7 antibody in particular (see references).
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