GNE mutations in an American family with quadriceps-sparing IBM and lack of mutations in s-IBM.

Analysis for GNE mutations was performed in an American, non-Iranian Jewish, family with quadriceps-sparing inclusion body myopathy (QS-IBM) and in 11 patients with sporadic IBM (s-IBM). Two novel nonallosteric site missense mutations were found in the QS-IBM kinship. No mutations were identified in s-IBM patients. After 8 years of follow-up and severe disease progression, the quadriceps muscle in the QS-IBM patient remains strong despite subclinical involvement documented with repeat MRI and muscle biopsy.