EOG. late onset

This form of vitelliform dystrophy (VMD4) is caused by heterozygous mutations in the IMPG1 gene (6q14.1).  However, rare families have been reported in which compound heterozygous or homozygous mutations have been found.  Some of the heterozygous parents of children with two mutations were found to have minor fundus changes such as tiny extramacular vitelliform spots in spite of being asymptomatic. This suggests that the transmission pattern of fundus changes may be both autosomal recessive and autosomal dominant. 

Genotyping has identified at least 5 forms of vitelliform macular dystrophy.  In addition to the iconic Best disease (VMD2, 153700) apparently first described by Friedreich Best in 1905 and now attributed to mutations in the Best1 gene, we know of at least 4 more and specific mutations have been identified in three.  No mutation or locus has yet been identified in VMD1 (153840) but it is likely a unique condition since mutations in other genes known to cause vitelliform dystrophy have been ruled out.  Other forms are VMD3 (608161) due to mutations in the PRPH2 gene, VMD4 described here, and VMD5 (616152) caused by mutations in the IMPG2 gene.