A Homozygous LAMA2 Mutation of c.818G＞A Caused Partial Merosin Deficiency in a Japanese Patient

A complete loss of merosin, which is encoded by LAMA2, causes congenital muscular dystrophy with leukoencephalopathy. Partial merosin deficiency can be caused not only by primarily LAMA2 mutations, but also secondarily by dystroglycanopathy. Although it can be molecularly diagnosed based on a genetic analysis, this method is labor-intensive because of its huge genome size. A 26-year-old male patient presented with mild muscular weakness, joint contractures, and epilepsy. Double immunofluorescence staining of a muscle biopsy specimen showed mislocalization of merosin, and a genetic analysis revealed a homozygous c.818G＞A (p.Arg273Lys) mutation in LAMA2. Double immunofluorescence staining and whole exome sequencing were useful for the diagnosis of partial merosin deficiency.