A novel PDGFRB sequence variant in a family with a mild form of primary familial brain calcification: a case report and a review of the literature

BACKGROUND: Primary familial brain calcification is a rare autosomal dominant or recessive neurodegenerative disease, characterized by bilateral brain calcifications in different areas of the brain. It is a clinically heterogeneous disease and patients are reported to exhibit a wide spectrum of neurological and psychiatric symptoms. Mutations in five genes have been identified so far including SLC20A2, PDGFRB, PDGFB, XPR1, and MYORG. PDGFRB encodes the platelet-derived growth factor receptor-beta, and is expressed in neurons, vascular smooth muscle cells and pericytes. Patients with a PDGFRB mutation seem to exhibit a milder phenotype and milder brain calcification on brain imaging than patients with SLC20A2 and PDGFB mutations. However, this is based on a few observations so far. CASE PRESENTATION: We present a Danish family with bilateral brain calcifications and mild clinical symptoms of primary familial brain calcification, segregating with a novel PDGFRB sequence variant: c.1834G > A; p.(Gly612Arg), detected by whole exome sequencing. The variant results in physiochemical changes at the amino acid level, and affects a highly conserved nucleotide as well as amino acid. It is located in the tyrosine kinase domain of PDGFRβ. Segregation analysis and in silico analyses predicted the missense variant to be disease causing. CONCLUSION: Our study confirms that PDGFRB mutation carriers in general have a mild clinical phenotype, and basal ganglia calcifications can be detected by a CT scan, also in asymptomatic mutation carriers.