Several of these genes are implicated in systemic disorders that can feature retinal involvement, including KIF11 (microcephaly–lymphedema–chorioretinal dysplasia), COL11A1 (Stickler syndrome), PHYH (Refsum disease), and TUBB4B (Leber congenital amaurosis with early-onset deafness). This evidence concerns the gene PHYH and microcephaly.