Basal Ganglia Calcification, Idiopathic, 2

Description

Familial idiopathic basal ganglia calcification (IBGC) is characterized by bilateral basal ganglia calcification and has been associated with a variety of neurologic, cognitive, and psychiatric abnormalities. However, some affected individuals may be clinically asymptomatic (summary by Volpato et al., 2009).

For a detailed phenotypic description and a discussion of genetic heterogeneity of IBGC, see IBGC1 (213600).

Clinical Features

Volpato et al. (2008) reported a large multigenerational Italian family from South Tyrol with IBGC. Twenty individuals over the age of 40 had positive CT scans revealing intracranial calcifications, with 14 having bilateral moderate to severe calcification of the basal ganglia, dentate nucleus, and subcortical white matter. Six had calcifications only in the pineal gland and/or choroid plexus. The calcification was age-dependent. Four individuals had hyperreflexia, 2 of whom also had gait and upper limb ataxia, slurred speech, and intellectual impairment. Four patients had short stature, 2 had short neck, and 1 had frontal hyperostosis and upper limb hypotrophy. In this family, the radiologic penetrance was much higher than the clinical penetrance, which was low. Linkage to the IBGC1 locus on 14q was excluded.

Mapping

By genomewide linkage analysis of the family reported by Volpato et al. (2008), Volpato et al. (2009) found evidence supporting a locus on chromosome 2q37 (maximum nonparametric lod score of 2.44 at D2S2973). This locus was downstream of the SLC19A3 gene (606152). Dai et al. (2010) referred to the locus on 2q37 as IBGC2.