Filtering of the exome data as above left just two possible candidate causal homozygous variants (both located in the largest stretch of shared homozygosity on chromosome 1) for further consideration: the first (c.625G>A [p.Val209Met]; RefSeq NM_006762.2) was in exon 7 of LAPTM5 (MIM 601476), which encodes a lysosomal transmembrane protein, and the second (c.225C>A [p.Asn75Lys]; RefSeq NM_002143.2) was in exon 2 of HPCA (MIM 142622), which encodes the neuronal calcium sensor (NCS) protein known as hippocalcin.