Myositis and muscular inclusions in Nakajo-Nishimura syndrome

Abstract

Background: Nakajo-Nishimura syndrome (NNS) is an autosomal recessive disease caused by a homozygous mutation in the human proteasome subunit beta type 8 gene (PSMB8) that encodes the immunoproteasome subunit β5i. Clinical features of NNS include periodic fever, skin rash and joint deformity. Patients often develop progressive muscle weakness and atrophy. Immunosuppressive therapy is often administered but not effective enough to prevent the progression of the disease. Skin pathological feature is characterized with inflammatory change and accumulation of ubiquitinated proteins. Reported muscle changes include mild inflammatory change, rimmed vacuole and fibrosis change, but there are limited reports about cilinicopahological comparison of muscle pathology in genetically confirmed cases.