Objective:

To identify clinical and pathologic features of SLONM and response to treatment.

Background:

Sporadic Late-Onset Nemaline Myopathy (SLONM) presents with progressive muscle weakness and is associated with normal or slightly elevated creatine kinase with myopathic changes on electromyography and nemaline rods on muscle biopsy. Nemaline rods are cytoplasmic inclusions formed by clusters of z-discs with variable aberrant actin cross-linking.

Design/Methods:

In a retrospective, observational study of patients identified by the presence of nemaline rods in muscle biopsies submitted to the University of Chicago Pathology Department, we analyzed clinical, histologic, pathologic, and treatment response.

Results:

Twelve of the 16 identified patients with myopathy and nemaline rods on muscle biopsy were female. The average age was 68. In all patients whose PFTs were tested, the FVC was reduced(58% +/- 5.4%) and 4/7 had evidence of LVH on echocardiogram. Most(7/9) did not have evidence of monoclonal gammopathy. Only two patients did, and the clonal population was IgG lambda. The majority did not have facial weakness(2/9), ophthalmoplegia(0/9), myalgias(4/9), fasciculations(1/9), or camptocormia(3/9) on initial presentation. Most patients had dysphagia(5/9), muscle atrophy(7/9), dyspnea(5/9), and diminished deep tendon reflexes(7/8) on examination. Eight patients had EMGs performed and nearly all(7/8) had a myopathic pattern. Three patients had genetic testing. Four patients were treated with IVIG, 4 with CS, 1 with PLEX, 3 with immunosuppression, and none with stem cell transplantation. All sixteen patients had evidence of myofiber atrophy. Most cases had fiber type grouping with minimal necrosis and evidence of regeneration but did not have interstitial fibrosis, adipose replacement, or inflammatory infiltration. Responses ranged from marked worsening and death to moderate improvement. 

Conclusions: