原発性シェーグレン症候群に合併した免疫介在性壊死性ミオパチーの1例

A Case of Immune-Mediated Necrotizing Myopathy Associated with Primary Sjögren Syndrome

症例は66歳女性で，四肢の筋力低下と労作時の呼吸困難を主訴に受診。神経学的に体幹，四肢近位筋に優位の筋力低下を認め，血中クレアチンキナーゼ（CK）値が2,747U/Lと高値を示した。筋生検で免疫介在性壊死性ミオパチーの所見を得たが，関連薬剤の内服歴はなく，抗SRP，抗HMGCR抗体は陰性であった。一方で抗SS-A抗体が53.2U/mLと陽性で唾液腺生検とシルマー試験からシェーグレン症候群と診断し，ステロイド療法にて筋力，CK値ともに改善。膠原病関連の筋合併症では本症例のように壊死性ミオパチーを認めることもあり，文献検索を含めて報告する。

Abstract

A 66-year-old woman visited our hospital complaining of shortness of breath during exertion and progressive weakness in all her limb muscles. On admission, we noted muscle weakness in her trunk and in her proximal limb muscles, although, her muscle MRI showed no remarkable findings. However, her serum CK level (2,747 U/L) was above the normal range. Histopathological examination of muscle biopsy, performed from the left biceps brachii muscle, revealed immune-mediated necrotizing myopathy (IMNM). Her serum samples were negative for myositis-associated autoantibodies (MAAs), anti-SRP, and HMGCR antibodies. However, as the anti-SS-A antibody level in her serum was high (53.2 U/mL), we conducted the salivary gland biopsy and the Schirmer test on her eyes. We found lymphocytes infiltration in her salivary gland tissue, and thus, she was diagnosed with primary Sjögren syndrome (SjS). We also observed necrotizing myopathy associated with the SjS. Following her treatment with oral steroids, her symptoms and CK level improved. Although, inflammatory myositis frequently occurs in association with general collagen diseases, necrotizing myopathy has rarely been observed secondary to SjS. We report here this rare case study along with the review of the relevant literature.

(Received June 24, 2020; Accepted October 12, 2020; Published February 1, 2021)