Abstract:

Autoantibodies to signal recognition particle have been associated with juvenile and adult-onset necrotizing myopathy. However, only a few teenage patients with anti-signal recognition particle myopathy have been reported, and to date, to our knowledge, no patient younger than 10 years has been documented. We describe 2 Japanese girls with anti-signal recognition particle myopathy who developed symptoms from the ages of 5 and 9 years, respectively. Both patients had progressive muscle weakness and atrophy without myalgia. Facioscapulohumeral muscular dystrophy was initially suspected because of asymmetric shoulder girdle muscle involvement in one patient, and limb girdle muscular dystrophy due to proximal limb muscle weakness in the other. There were no extramuscular manifestations, including fever or arthritis. Serum creatine kinase levels were elevated to 2,467-4,629 IU/L. Results of muscle biopsy revealed necrotizing myopathy with minimal to mild endomysial fibrosis but without inflammatory infiltrates. Immunosuppressive agents were not effective for muscle weakness, resulting in marked disability. Anti-signal recognition particle myopathy can occur in the first decade of life and should be included in the differential diagnosis for children with progressive limb girdle muscle weakness and high creatine kinase levels.

日本語要旨:

10歳未満発症のSRPミオパチー例2例を報告した。発症年齢はそれぞれ5歳と9歳であった。SRPミオパチーは通常成人が罹患し、10歳未満で発症することは極めて希である。両例とも進行性の筋萎縮を示し、顔面肩甲上腕型筋ジストロフィーと肢帯型筋ジストロフィーが当初の鑑別診断であった。筋組織学的検索では、壊死・再生線維を認めたが、リンパ球浸潤は認めなかった。進行性筋萎縮を示す小児例においてもSRPミオパチーを鑑別に上げる必要がある。