P.4.12 Association of two mutations in the RYR1 gene in central core disease: Recessive or modifying effect?

Abstract

Central core disease (CCD) is a congenital myopathy, characterized by the presence of central core-like areas in muscle fibers. Patients usually have mild or moderate axial and proximal weakness, hypotonia and motor developmental delay. CCD is associated with mutations in human RYR1 gene, which encodes a calcium release channel known as ryanodine receptor (RyR1). Here we present a family diagnosed with CCD with distinct phenotypes. A 48-year old female was referred to our service with clinical features suggesting a congenital myopathy. Histological analysis confirmed the diagnosis of CCD. Nine exons from the C-terminal region of RYR1 were screened for mutations in the index case. Two different missense mutations were identified: c.14256 A>C in exon 98 and c.14693 T>C in exon 102. Trans position of the 2 mutations was confirmed because patient's daughter, mother and sister carried the exon 98 mutation, but not the one in exon 102. The mutation in exon 102 have already been described as pathogenic, and is compatible with both severe and mild phenotypes, observed as intra and inter family variability. On the other hand, the c.14256 A>C mutation in exon 98 is a single nucleotide variation and its clinical significance is still untested. Considering the fact that patient's relatives showed no CCD phenotype, it could be inferred that this polymorphism alone is not responsible for the disease. Moreover, the effect of association of this polymorphism to exon 102's pathogenic mutation is not clear. Further studies about patients with both exon 98 polymorphism and exon 102 mutation could help establishing a better relation between these two findings. The case described above illustrates the present reality where new methods for wide genome screening are becoming more accessible and able to identify a great variety of mutations and polymorphisms in patients and their families. FAPESP-CEPID, CNPq-INCT, FINEP.