In a large consanguineous Bedouin family, probably from Kuwait, with bilateral frontoparietal polymicrogyria, Piao et al. (2004) identified a C>T transition at nucleotide 1693 of the GPR56 gene, resulting in the substitution of the conserved amino acid (p.R565W). This pedigree consisted of two nuclear families that were distantly related to one another; the two affected individuals from the first family had first-cousin parents, and the affected individual from the second family had consanguineous parents whose exact relationship was unknown. In addition, in one child, born to first cousin Arab parents, with bilateral frontoparietal polymicrogyria, Piao et al. (2004) identified homozygosity for a G>C transversion at nucleotide 272 of exon 3 of the GPR56 gene, resulting in a cysteine-serine substitution at codon 91 (p.C91S).

Straussberg et al. (1996) described a Palestinian family in which the parents were first cousins and three of the siblings suffered from moderate mental retardation, pachygyria and strabismus. In 2002, Piao et al. described the clinical and genetic features of the autosomal recessive stereotyped form of polymicrogyria in two consanguineous families from Palestine, includeing the one described by Straussberg et al. (1996). 

Chang et al. (2003) reported 19 patients from 10 kindreds with apparent autosomal recessive bilateral frontoparietal polymicrogyria. Included were the 2 families reported previously by Piao et al. (2002).  The authors noted that the syndrome of bilateral frontoparietal polymicrogyria appears to be very common and may be frequently misdiagnosed.

In a consanguineous Qatari family with two children with bilateral frontoparietal polymicrogyria, Piao et al. (2004) identified a C>T transition at nucleotide 112 of the GPR56 gene, resulting in an arg-trp substitution at codon 38 (p.R38W) and probably affecting ligand binding by GPR56.

Sztriha and Nork (2002) reported a third case of bilateral symmetrical frontoparietal polymicrogyria in an 8-year-old-boy who was born at term to consanguineous parents of United Arab Emirates origin.