Biallelic variants in the minor spliceosomal gene RNU4ATAC were successively identified in Taybi-Linder/MOPD1 (Microcephalic osteodysplastic primordial dwarfism type I), Roifman, and Lowry-Wood syndromes, characterized by variable microcephaly, short stature, neurodevelopmental impairment, skeletal dysplasia, and immunodeficiency. Two-thirds of the reported individuals present with Taybi-Linder syndrome, the first described and most severe form.