Linkage to MFRP was excluded in all 6 consanguineous families. Only 1 run of homozygosity was shared between 5 of the 6 families, and linkage to this locus on chromosome 2q37 was confirmed with a logarithm of odds score of 5.73 (Figure 1). The locus (17.2 megabases) is flanked by single-nucleotide polymorphisms rs6716235 and rs13009438. Interestingly, alignment of the run of homozygosity in the 5 families followed by PCR confirmation of the flanking single-nucleotide polymorphisms revealed a much narrower interval of 894 965 base pairs (chr2:232,012,660-232,907,624) bordered by rs6753112 and rs2697798 (eFigure). Haplotype analysis of the minimal run of homozygosity suggested that a common founder mutation was unlikely (Figure 1). No pathogenic sequence variants were identified in any of the 8 genes (NCL, C2orf52, NMUR1, C2orf57, PTMA, PDE6D, COPS7B, and NPPC) contained within this interval. Reverse transcription–PCR revealed normal splicing, and sequencing of the transcripts further ruled out the presence of coding mutations. Linkage to MFRP and to this locus was excluded in family 6. Interestingly, a novel homozygous missense mutation in MFRP (c.1549C>T, p.R518W) was identified in the South African family, which displayed the typical PM phenotype (Figure 2). The PolyPhen Web tool (http://genetics.bwh.harvard.edu/pph/) predicted that this mutation, which replaces a highly conserved arginine residue, is probably damaging with a score of 2.495.