Distal myopathy with rimmed vacuoles: Report on clinical characteristics in 23 cases

Background: Distal myopathy with rimmed vacuoles (DMRV) is an autosomal recessive (AR) myopathy characterized clinically by the preferential involvement of the tibialis anterior and has been reported predominantly in the Japanese population.
Materials and Methods: A case series of DMRV patients seen over a period of 3 years at a tertiary national referral center for neurological disorders in south India.
Results: We describe the clinical characteristics, muscle magnetic resonance imaging (MRI) findings and classical histopathological feature in 23 patients. There were 12 men and 11 women. Mean age of onset was 27.04 ± 6.35 years (10-39 years). Onset was in the second or third decade in a majority. Mean age at presentation was 33.95 ± 6.35 years (25-48 years). Mean duration of illness was 6.74 ± 4.8 years (1-18 years). Consanguinity was reported in eight (34.8%) patients. The predominant and initial manifestation was bilateral foot drop in all patients. Muscle MRI demonstrated classical involvement of the anterior compartment muscles of the lower legs and the posterior compartment muscles of the thighs and the quadriceps was normal in all. Muscle histopathology showed numerous fibers containing rimmed vacuoles. Necrotic fibers or phagocytosis or regenerating fibers were rarely noted or were absent.
Conclusions: DMRV is a rare AR myopathy. The disorder presents as progressive foot drop and hence has many differential diagnoses. It is easily mistaken as neuropathy of hereditary nature and hence it is extremely important to recognize the preferential muscle involvement and characterize the phenotype. This is the first report from India with patients having characteristic phenotype of Nonaka′s/AR hereditary inclusion body myopathy with quadriceps sparing, and all were confirmed by histopathology.