OFD1 and retinitis pigmentosa 23: OFD1 mutations have also been reported in males in X-linked recessive conditions, namely (1) a mental retardation syndrome comprising macrocephaly and ciliary dysfunction [23] mapping to the same locus as Simpson–Golabi–Behemel syndrome type 2 (SGBS2); (2) Joubert syndrome (JS) patients (JBT10) [24–26] and (3) retinitis pigmentosa (RP23) [27].