JIMD Reports, Volume 38

Panicucci, Chiara, Fiorillo, Chiara, Moro, Francesca, Astrea, Guja, Brisca, Giacomo, Trucco, Federica, Pedemonte, Marina, Lanteri, Paola, Sciarretta, Lucia, Minetti, Carlo, Santorelli, Filippo M, Bruno, Claudio, Chiara Panicucci, Chiara Fiorillo, Francesca Moro, Guja Astrea, Giacomo Brisca, Federica Trucco, Marina Pedemonte, Paola Lanteri, Lucia Sciarretta, Carlo Minetti, Filippo M. Santorelli, Claudio Bruno, Santorelli, Filippo M.

Mutations in the guanosine diphosphate mannose (GDP-mannose) pyrophosphorylase B (GMPPB) gene encoding a key enzyme of the glycosylation pathway have been described in families with congenital (CMD) and limb girdle (LGMD) muscular dystrophy with reduced alpha-dystroglycan (α-DG) at muscle biopsy.Patients typically display a combined phenotype of muscular dystrophy, brain malformations, and generalized epilepsy. However, a wide spectrum of clinical severity has been described ranging from classical CMD presentation to children with mild, yet progressive LGMD with or without intellectual disability. Cardiac involvement, including a long QT interval and left ventricular dilatation, has also been described in four cases.Two missense mutations in GMPPB gene, one novel and one already reported, have been identified in a 21-year-old man presenting with elevated CK (38,650 UI/L; normal values <150 UI/L) without overt muscle weakness. Major complaints included limb myalgia, exercise intolerance, and several episodes of myoglobinuria consistent with a form of metabolic myopathy. Muscle biopsy showed only minimal alterations, whereas a marked reduction of glycosylated α-DG was evident.This case further expands the phenotypic spectrum of GMPPB mutations and highlights the importance of exhaustive molecular characterization of patients with reduced glycosylation of α-DG at muscle biopsy.