Atypical distribution of muscular atrophy in a 29-year-old man with polymyositis and anti-SRP antibodies].

A 29-year-old man developed muscle weakness in the neck at age 27. An increasing serum creatine kinase (CK) activity was detected. The first examination at our hospital revealed severe muscular atrophy at the front of the neck. Subsequently, muscular atrophy and weakness developed in the shoulders and upper extremities with an increasing serum CK level, which reached 9,159 IU/l. Needle electromyography (EMG) was not able to reveal typical myopathic change represented low-amplitude motor unit potentials (MUPs) in the proximal parts of the upper and lower extremities at the first examination, but in the course of the disease, the MUPs amplitude decrease in the same muscles. Serum examination gave a positive result for anti-signal recognition particle (SRP) antibodies. A biopsy of the deltoid muscle revealed necrotizing myopathy including small angular fiber-like atrophy without inflammatory cell infiltration or fibrotic proliferation. He was treated with prednisolone and tacrolimus with the diagnosis of polymyositis. The characteristic feature in this patient is that muscular atrophy and weakness were mainly observed in the neck. Moreover, the neurogenic changes on EMG in the early stage are also observed on atypical. Polymyositis with anti-SRP antibodies has the distinctive feature of typical polymyositis with cellular infiltration clinically and pathologically. In this respect, this case has striking and suggestive features of polymyositis with anti-SRP antibodies.

Citation

Michiaki Miwa, Yuki Nakamura, Takamura Nagasaka, Kazumasa Shindo, Yoshihisa Takiyama. Atypical distribution of muscular atrophy in a 29-year-old man with polymyositis and anti-SRP antibodies]. Rinshō shinkeigaku = Clinical neurology. 2012;52(4):234-8

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PMID: 22531655

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