Homozygosity mapping of familial glioma in Northern Sweden.

About 5% of glioma cases are familial. Most glioma families are not ascribed to the well-known glioma predisposing syndromes. One segregation analysis has supported an autosomal recessive gene in glioma families, which could be studied by homozygosity mapping. The ancestors of seven glioma families from the northern region of Sweden were traced through genealogical databases. A common ancestor and inbreeding were traced to give support to an autosomal recessive gene. Homozygosity mapping was performed with a genome-wide scan of 811 markers with linkage calculations. The families were geographically mapped to see if familial glioma was more common in northern compared with southern Sweden. Three of the seven families were remotely related. Homozygosity mapping did not reveal any allele homozygous for all three families. However, there was a geographical clustering of glioma families in the northern region of Sweden. A non-parametric analysis showed an allele-sharing LOD score of 1.05 for marker D1S196 on chromosome 1q23. Genealogical studies linking glioma families might be a tool for linkage in a small set of families. This study did not support an autosomal recessive gene, implicating a low penetrant dominant gene as a possible explanation to the glioma family clustering.