BACKGROUND
Mutations in the kinesin family member 11 (KIF11) gene have been recently identified in several families worldwide. This gene plays a crucial role in cell division, chromosomal positioning, and separation. KIF11 mutations are associated clinically with microcephaly with or without chorioretinopathy, lymphedema, or intellectual disability (MCLMR). It is an autosomal dominant disorder with reduced penetrance, and few reports in the literature describe its phenotypic associations.
CASE REPORT
We present the case a 39-year-old man from the Kingdom of Saudi Arabia with a known history of nyctalopia who was diagnosed with retinitis pigmentosa in early childhood. He experienced a profound decrease in visual acuity in both eyes, accompanied by a severely reduced rod response and mixed cone responses on full-field electroretinography. Fundus examination in both eyes showed a pale disc, diffuse retinal atrophy extensively involving the macula, mild blood vessel attenuation, pigment clumping with bone spicules, islands of peripheral and mid-peripheral chorioretinal atrophy, and lattice degeneration at the periphery. Optical coherence tomography revealed outer retinal atrophy with loss of the ellipsoid zone. Targeted next-generation sequencing using a vision/retinal dystrophy gene panel identified a heterozygous frameshift variant in KIF11 (NM_004523.4: c.535del; p.(Ser179Leufs*16)), classified as likely pathogenic according to ACMG/AMP/ClinGen SVI guidelines. The variant was absent from population databases (gnomAD, ESP, 1000 Genomes) and, to the best of our knowledge, has not been previously reported in the literature. The patient was diagnosed with KIF11-related MCLMR syndrome, presenting with microcephaly and chorioretinal atrophy.
CONCLUSIONS
Mutations in KIF11 are uncommon. Due to its reduced penetrance, individuals with this mutation may present mainly with microcephaly with or without chorioretinopathy, lymphedema, intellectual disability, or even without any clinical features. Early diagnosis of the disease is crucial for multidisciplinary management and genetic counseling.

Keywords: Lymphedema; Microcephaly; Retinal Dystrophies; Ophthalmology; Chorioretinopathy; KIF11 protein, human; Genetic Predisposition to Disease; Case Reports