Sporadic late-onset nemaline myopathy in a patient with primary Sjögren’s syndrome

Abstract

Nemaline myopathy is a rare disorder defined by the presence of nemaline rods in muscle fibers. Adult forms are known as sporadic late-onset nemaline myopathy (SLONM) [1, 2]. We report the first case of SLONM associated with primary Sjogren’s syndrome (PSjS). A 58-year-old woman without family history of musculoskeletal disease presented with progressive muscle weakness over the course of 2 years. She had severe difficulty walking and holding her head up, and was unable to rise from a chair. She also presented with dry eyes and mouth. Laboratory investigations revealed normal CK, absence of anti-AChR antibodies, and negative viral serology, including HIV. Level of IgG was mildly elevated without monoclonal gammopathy of undetermined significance (MGUS). Anti-SS-A/Ro antibodies were elevated at 295 U/ml. A salivary-gland-biopsy revealed lymphocytic sialoadenitis. Electromyography revealed myopathic motor unit potentials with fibrillation potentials and positive sharp waves (PSW) in the four limbs. Nerve conduction studies were normal. Left-quadriceps-muscle-biopsy revealed variation of muscle fiber diameter with scattered atrophic fibers, and no inflammatory cell infiltration. On hematoxylin-eosinstaining, some muscle fibers contained eosinophilic granules. Modified Gomori-trichrome-stained section showed variable rods in more than half of the muscle fibers. Only a few rods were crisply rod-shaped and many were somewhat irregular and punctuate. Severely affected fibers were small and occasionally vacuolated. NADH-TR-stained section revealed lobulated fibers, many of them were type 1 fibers. Fiber type proportions were normal. Electronmicroscopic image showed variable rods, some arising from the Z-discs (Fig. 1). No amyloid was detected. Genetic analysis was not performed. A diagnosis of SLONM with PSjS was made. Neck weakness and sicca syndrome were improved with prednisolone. Residual weakness was improved with intravenous immunoglobulin (IVIg, 0.4 g/kg/day for 5 days). She was eventually able to walk with a cane and rise from a chair without assistance. Fibrillation potentials and PSW in electromyography disappeared. Anti-SS-A/Ro antibodies were decreased at 49.9 U/ml. Symptomatic myopathy in PSjS is rarely reported in association with hypothyroidism or renal tubular acidosis [3–5]. Myositis is noted in secondary SjS patients, although muscle biopsy findings are quite variable. In our patient, these conditions were excluded by laboratory examinations. Etiology of SLONM is unclear. Because some cases of SLONM are associated with MGUS [2, 6, 7], and some occur in the early immunocompetent period of HIV infection [8, 9], an immune dysregulation or an unrecognized viral trigger have been suspected [2, 10]. Our patient developed muscle weakness and sicca syndrome simultaneously, which improved with immunotherapy. Nemaline rods were the predominant findings and features of other etiologies were absent. We believe the primary diagnosis to be SLONM, and suspect that immunological abnormalities may have played a role in the development of both PSjS and SLONM. HIV-associated SLONM has been noted to respond to therapy with prednisone or plasmapheresis [11–13], or a combination of IVIg [14], whereas a concomitant MGUS leads to a very poor prognosis [2]. However, two patients with non-HIV SLONM/MGUS were recently reported to M. Suzuki (&) Y. Shimizu M. Takeuchi M. Kobayashi M. Iwata S. Uchiyama Department of Neurology, Tokyo Women’s Medical University, 8-1 Kawadacho Shinjuku-ku, Tokyo 162-8666, Japan e-mail: suzukimiki@nij.twmu.ac.jp