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

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 (2,747U/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 (53.2U/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).