Calcifications idiopathiques des noyaux gris centraux (maladie de Fahr)

Idiopathic basal ganglia calcification, commonly known as Fahr's disease, is characterized by the presence of cerebral calcifications involving at least the basal ganglia, with no cause after extensive clinical and biological etiological assessment. The signs associated with the disease are diverse: movement disorders, psychiatric signs, cognitive impairment, dysarthria, gait disorders, ataxia and cerebellar syndrome, pyramidal signs, and seizures. There is a wide intra- and inter-familial clinical diversity and some individuals may remain asymptomatic. Sporadic and familial presentations are possible, mainly with an autosomal dominant pattern of inheritance. Three causative genes have been recently reported: SLC20A2, which encodes the inorganic phosphate transporter PiT2, PDGFRB which encodes the transmembrane receptor PDGFRβ, and PDGFB, which encodes PDGF-B, the main ligand of PDGFRβ. The pathophysiological hypotheses are in favor of a disorder of the inorganic phosphate metabolism in intracerebral small vessels and perivascular spaces and of an alteration of the brain-blood barrier. No specific treatment is available. Symptomatic treatments may be proposed on a case-by-case basis. Genetic counseling is difficult because of a incomplete clinical penetrance.