STAC3 related congenital myopathy: A case series of seven Comorian patients

The Bailey-Bloch congenital myopathy, also known as Native American myopathy (NAM), is an autosomal recessive congenital myopathy first reported in the Lumbee tribe people settled in North Carolina (USA), and characterized by congenital weakness and arthrogryposis, cleft palate, ptosis, short stature, kyphoscoliosis, talipes deformities, and susceptibility to malignant hyperthermia (MH) triggered by anesthesia. NAM is linked to STAC3 gene coding for a component of excitation-contraction coupling in skeletal muscles. A homozygous missense variant (c.851G > C; p.Trp284Ser) in STAC3 segregated with NAM in the Lumbee families. Non-Native American patients with STAC3 related congenital myopathy, and with other various variants of STAC3 have been reported. Here, we present seven patients from the Comoros Islands (located in the Mozambique Channel) diagnosed with STAC3 related congenital myopathy and having the recurrent variant identified in the Lumbee people. The series is the second largest series of patients having STAC3 related congenital myopathy with a shared ethnicity after le Lumbee series. Local history and geography may explain the overrepresentation of NAM in the Comorian Archipelago with a founder effect. Further researches would be necessary for the understanding of the onset of the NAM in Comorian population as search of the "classical" STAC3 variant in East African population, and haplotypes comparison between Comorian and Lumbee patients.