Further Expansion of the Mutational Spectrum of 3MC Syndrome: A Novel MASP1 Pathogenic Variant in a Male Patient.

The 3MC syndrome is a rare autosomal recessive syndrome characterized by facial dysmorphism, multiple congenital abnormalities, and postnatal growth deficiency. Hypertelorism, blepharophimosis, blepharoptosis, high-arched eyebrows, and cleft lip/palate compose the facial gestalt, which is the key component for diagnosing the syndrome. Biallelic pathogenic variants in MASP1, COLEC11, and COLEC10 are responsible for 3MC syndrome in which both genotypic and phenotypic heterogeneity is described. To date, 16 homozygous/compound heterozygous pathogenic variations in 27 patients from 22 families have been reported in the MASP1 gene associated with 3MC syndrome. Here, we report a male patient with a novel homozygous pathogenic variant in MASP1 in whom macrocephaly, pyloric stenosis, and prenatal findings including polyhydramnios, aortic dilatation, and intracranial cysts beside the distinctive facial features were detected. Reporting detailed clinical and molecular findings in patients is pivotal in terms of enabling the phenotypic and genotypic spectrum of this rare syndrome to be delineated.