[Head drop syndrome in a patient with immune-mediated necrotizing myopathy with anti-signal recognition particle antibody: a case report].

We report an 87-year-old female patient who presented a dropped head and progressive weakness in proximal muscles over five months. The value of serum creatine kinase was 2,708 IU/l and the antibody against signal recognition particle (SRP) was detected by means of immunoprecipitation. The computed tomography of skeletal muscles revealed atrophy and fatty degeneration preferentially in the neck extensors and paraspinal muscles. The biopsied specimen of the deltoid muscle showed necrotic fibers scattered in fascicles with marked myophagia. The mononuclear cells in necrotic fibers were positive against CD68, leading to the diagnosis of immune-mediated necrotizing myopathy. We hypothesize that a group of patients with necrotizing myopathy can present a preferential involvement in neck extensors resulting in dropped head syndrome.