ACTA1-myopathy with prominent finger flexor weakness and rimmed vacuoles

Actinopathy is a group of clinically and pathologically heterogeneous myopathies due to mutations in the skeletal muscle sarcomeric α-actin 1-encoding gene (ACTA1). Disease-onset spans from prenatal life to adulthood and weakness can preferentially affect proximal or distal muscles. Myopathological findings include a spectrum of structural abnormalities with nemaline rods being the most common. We report a daughter and father with prominent finger flexors and/or quadriceps involvement. Muscle biopsies revealed rimmed vacuoles in both patients, associated with type 1 fiber atrophy in the daughter, and nemaline rods in the father. Next generation sequencing identified a novel dominant ACTA1 variant, c.149G > A (p.Gly50Asp) in both individuals and no abnormal variants in vacuolar myopathy-associated genes. Our findings expand the clinico-pathological spectrum of actinopathy.