We report three patients with a predominantly proximal myopathy due to p.A193T mutation in the actin-binding domain of FLNC, which has so far only been associated with a distal myopathy.
A frameshift mutation in the filamin C rod domain causing haploinsufficiency was also found responsible for distal myopathy with some myofibrillar changes but no protein aggregation typical of myofibrillar myopathies.
We conclude filamin C ABD mutations cause a recognizable distal myopathy, most likely through increased actin affinity, similar to the pathological mechanism of filamin A and filamin B ABD mutations.