Mutations in SEPN1 have been associated with three autosomal recessive congenital myopathies, including rigid spine muscular dystrophy, multiminicore disease and desmin-related myopathy with Mallory body-like inclusions. These disorders constitute the SEPN1 related myopathies (SEPN-RM). On the basis of clinical and laboratory features compatible with SEPN-RM, we performed mutation analysis of SEPN1 in 11 unrelated patients and found one case with pathogenic mutations. He showed early onset axial muscle weakness and developed scoliosis with respiratory insufficiency. Muscle biopsy showed increased variability of fiber size and slight, focal increase of connective tissue. A few fibers showed mini-core changes. SEPN1 mutation analysis revealed that the patient was a compound heterozygote: a previously described insertion (713-714 insA), and a novel nonsense mutation (R439stop).