An Update on Primary Familial Brain Calcification

Patients with primary familial brain calcifications (PFBC) present bilateral calcifications, often affecting basal ganglia, thalamus, and cerebellum, inherited in an autosomal dominant pattern of segregation. Affected individuals display a wide variety of motor and cognitive impairments such as parkinsonism, dystonia, migraine, dementia, psychosis, and mood symptoms. Worldwide growth in the availability of neuroimaging procedures, combined with careful screening of patients and their relatives, has increased detection of PFBC. Recently, mutations in the SLC20A2 gene coding for the inorganic phosphate transporter PiT2 were linked to PFBC, thereby implicating impaired phosphate transport as an underlying disease mechanism. To date, around 20 families of various ethnicities carry different mutations in SLC20A2 correlate with similar to 40% of PFBC cases. More recently, two French families were recently reported with mutations in PDGFRB: c.1973 T>C, p.L658P and c.2959C>T, p.R987W, a class Ill tyrosine kinase receptor. Six other families were found with mutations in PDGFB, and, in general, mutations at the PDGF pathway add a new dimension to the physiopathology of PFBC so far explained by a disturbance in phosphate homeostasis with SLC20A2. The identification of SLC20A2, PDGFRB, and PDGFB provides a new avenue for potential treatments based on compounds such as bisphosphonates and those modulating the PDGFB pathway.