Genetic Microcephaly in a Saudi Population: Unique Spectrum of Affected Genes Including a Novel One

Background: Genetic microcephaly is linked to an increased risk of developmental disabilities, epilepsy, and motor impairment. The aim of this study is to describe the spectrum of identifiable genetic etiologies, clinical characteristics, and radiologic features of genetic microcephaly in patients referred to a tertiary center in Saudi Arabia. Method: This is a retrospective chart review study of all patients with identifiable genetic microcephaly presenting to a tertiary center in Saudi Arabia. The patients' demographics, clinical, laboratory, radiologic, and molecular findings were collected. Results: Of the total 128 cases referred, 52 cases (40%) had identifiable genetic causes. Monogenic disorders were found in 48 cases (92%), whereas chromosomal disorders were found in only 4 cases (8%). Developmental disability was observed in 40 cases (84%), whereas only 8 cases (16%) had borderline IQ or mild developmental delay. Epilepsy was seen in 29 cases (56%), and motor impairment was seen in 26 cases (50%). Brain magnetic resonance imaging (MRI) revealed abnormalities in 26 (50%) of the cohort. Hereditary neurometabolic disorders were seen in 7 (15%) of the 48 cases with monogenic disorders. The most common gene defect was ASPM, which is responsible for primary microcephaly type 5 and was seen in 10 cases (19%). A novel PLK1 gene pathogenic mutation was seen in 3 cases (6%). Conclusion: Single gene defect is common in this Saudi population, with the ASPM gene being the most common. Hereditary neurometabolic disorders are a common cause of genetic microcephaly. Furthermore, we propose the PKL1 gene mutation as a possible novel cause of genetic microcephaly.