An Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM) linked to chromosome 9p1.

We report an Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM). The patients (two second cousins) developed a slowly progressive distal and proximal myopathy with complete sparing of the quadriceps. Muscle biopsy showed rimmed vacuoles in numerous muscle fibers, and electron microscopy documented accumulation of 15-21 nm filaments. DNA analysis established linkage to 9p1 and haplotype analysis revealed that the patients shared a recombined common haplotype. The gene locus of ARQS-IBM was initially mapped to chromosome 9p1-q1 in families of Iranian-Jewish origin and later confirmed in a few other ethnic groups. This is the first report of Italian patients with ARQS-IBM showing positive linkage to chromosome 9p1. Our data suggest that patients having distal and proximal myopathy with rimmed vacuoles and possible recessive inheritance, often classified as distal myopathies, should be thoroughly investigated according to the diagnostic criteria of h-IBM and, when positive, studied for linkage to chromosome 9p1.