We herein report a 32-year-old woman with adult-onset reducing body myopathy (RBM) who had a mutation in the four-and-a-half LIM domain 1 gene (FHL1) and showed a marked asymmetrical involvement of sternocleidomastoid and trapezius muscles. At 30 years of age she noticed bilateral foot drop, and over the next two years developed difficulty raising her right arm. At 32 years of age she was admitted to our hospital for a diagnostic evaluation. Neurological examination showed moderate weakness and atrophy of her right sternocleidomastoid muscle, right trapezius muscle, and bilateral upper proximal muscles. There were severe weakness and atrophy of her bilateral tibialis anterior muscles. Her deep tendon reflexes were hypoactive in her upper extremities. Her serum creatine kinase level was mildly increased. Muscle biopsy specimens from the left tibialis anterior muscle revealed marked variation in fiber size, some necrotic or regenerating fibers, and reducing bodies. Gene analysis of FHL1 demonstrated a mutation: a heterozygous missense mutation of c.377G>A (p. C126T) in FHL1. Compared with previous adult-onset RBM cases harboring mutations in FHL1, our case was characterized by asymmetrical atrophy of the sternocleidomastoid and trapezius muscles.
Keywords: Adult onset; FHL1; Gene; Mutation; Reducing body myopathy.
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