Scapuloperoneal muscular dystrophy phenotype due to TRIM32-sarcotubular myopathy in South Dakota Hutterite

Scapuloperoneal muscular dystrophy is a group of genetically heterogeneous disorders that share the phenotype of progressive weakness of scapular and anterior distal leg muscles. Recessive mutations in C-terminal domains of TRIM32 result in limb-girdle muscular dystrophy 2H and sarcotubular myopathy, a rare congenital myopathy commonly seen in Hutterites. A scapuloperoneal phenotype has never been reported in sarcotubular myopathy. We here report a 23-year-old Hutterite man with a one-year history of progressive weakness predominantly involving the anterior tibial and left scapular muscles, and hyperCKemia. Biopsy of the anterior tibial muscle showed an active myopathy with non-rimmed vacuoles and mild denervation atrophy associated with reinnervation. The vacuoles are similar to those described in sarcotubular myopathy. TRIM32 sequencing revealed the common c.1459G>A mutation at homozygosity. A search for mutations in TRIM32 should be considered in patients with scapuloperoneal muscular dystrophy, and especially in patients of Hutterite origin or with an atypical vacuolar myopathy.