Objective:

Our objective was to describe an atypical presentation of adult-onset Bethlem myopathy in a Puerto Rican woman whose clinical and radiologic features initially suggested possible demyelinating etiology.

Background:

Bethlem myopathy (BM) is an uncommon, collagen-VI related muscular dystrophy caused by mutations in COL6A1, COL6A2 or COL6A3. It normally presents during childhood with symptoms such as progressive proximal weakness and joint contractures, though rare adult-onset cases do occur. Central nervous system demyelination and ocular symptoms are atypical of this disorder, and patients with MRI nonspecific white-matter lesions combined with optic dysfunction can be misdiagnosed with a demyelinating disorder. Few cases regarding Latino populations have been reported, demonstrating a clear research gap in an already rare disorder.

Design/Methods:

A 44-year old woman presented with upper extremity fatigability, “Christmas-tree” cataracts, bilateral hand contractions and progressive visual deterioration . Brain MRI revealed nonspecific left frontal subcortical and bilateral periventricular T2 hyperintensities. No spinal cord involvement was observed in MRI. Lumbar puncture was negative for CSF-restricted oligoclonal bands and showed a normal Igg index. Organic acids test was also negative. Genetic sequencing revealed a pathogenic COL6A3 variant: c.1708C>T (p.Gln570*). Additionally, it also uncovered several mutations related to muscular dystrophy type 2 (DM2). Whole exosome sequencing and a muscle biopsy are scheduled for December to further characterize the condition.

Results:

The combination of MRI abnormalities, ocular symptoms and slow myopathic progression provided suspicions of a demyelinating disorder, but the absence of oligoclonal bands and genetic testing showing a nonsense COL63A variant confirmed the diagnosis of Bethlem myopathy.

Conclusions: