HACD1-related congenital myopathy skeletal muscle MRI findings in a Brazilian cohort.

HACD1-related congenital myopathy is an ultra-rare congenital myopathy recently described in families from the Middle East or Asia. Clinical phenotype has been described, but little is known about the pattern of muscle MRI abnormalities. We describe four Brazilian patients from unrelated families including not only clinico-pathological, but also muscle MRI findings. All patients shared the known pattern of early onset of motor deficits combined with respiratory distress, later followed by remarkable improvement. Muscle biopsy revealed congenital fiber type disproportion. The same pathogenic biallelic HACD1 variant was found in all cases (c.373_375+2delGAGGT). Three out of the 4 patients underwent muscle MRI, which revealed symmetrical fatty infiltration predominantly affecting the pelvic girdle and the posterior compartment of lower limbs; anterior compartment of thighs and legs was essentially preserved. The current description expands the geographical landscape of the disease and refines its phenotypical characterization by presenting the pattern of muscle MRI abnormalities.