Muscle magnetic resonance imaging and histopathology in ACTA1‐ related congenital nemaline myopathy

: Muscle biopsy is usually diagnostic in nemaline myopathy (NM), but some patients may show nonspecific findings, leading to pitfalls in diagnosis. Muscle MRI is a helpful complementary tool. Methods : We assessed the clinical, histopathological, MRI, and molecular findings in a 19‐year‐old patient with NM in whom 2 muscle biopsies with ultrastructural examination showed no nemaline bodies. We analyzed the degree and pattern of muscle MRI involvement of the entire body, including the tongue and pectoral muscles. Results : Muscle MRI abnormalities in sartorius, adductor magnus, and anterior compartment muscles of the leg suggested NM. A previously unreported fatty infiltration of the tongue was found. A third biopsy after the muscle MRI showed scant nemaline bodies. A novel heterozygous de novo ACTA1 c.611C>T/p.Thr204Ile mutation was detected. Conclusions : We highlight the contribution of muscle imaging in addressing the genetic diagnosis of ACTA1 ‐related NM. Muscle Nerve 50: 1011–1016, 2014