Co-existence of mutations in PRRT2 and ABCC6 genes in a Turkish family

Abstract

Paroxysmal kinesigenic choreoathetosis (PKC) is an inherited disorder with an autosomal dominant mode of inheritance, caused mostly by the mutations in PRRT2 (proline-rich transmembrane protein-2) gene, located on chromosome 16. Pseudoxanthoma elasticum (PXE) is a hereditary metabolic disease with autosomal recessive inheritance resulting from the mutations in the ABCC6 (ATP-Binding Cassette, Subfamily C, Member 6) gene, located also on chromosome 16. Here we present a female patient with familial paroxysmal kinesigenic dyskinesia and benign familial infantile convulsions (BFIC), in whom both a heterozygous truncating frameshift mutation in the PRRT2 gene and a heterozygous missense mutation in the ABCC6 gene were demonstrated. The co-existence of these two mutations has not been reported in the literature. Although the clinical symptomatology of PXE was not present in our patient, some family members of our index case had. Here we present a Turkish family with two different mutations on the same chromosome, namely PRRT2 and ABCC6 mutations. However, because these two mutations have separate parental inheritance and are not in linkage disequilibrium, the co-existence was reported as co-incidental.