microcephalic osteodysplastic primordial dwarfism type I (MONDO_0008871) is a microcephalic osteodysplastic primordial dwarfism that has material basis in homozygous or compound heterozygous mutation in the RNU4ATAC gene, encoding a small nuclear RNA (snRNA) component of the U12-dependent (minor) spliceosome, on chromosome 2q14.2. It is characterized by dwarfism, microcephaly, and neurologic abnormalities, including mental retardation, brain malformations, and ocular, auditory sensory deficits. Also known as: MOPD 1, MOPD1, Taybi-Linder syndrome, brachymelic primordial dwarfism, cephaloskeletal dysplasia, low-birth-weight dwarfism with skeletal dysplasia, microcephalic osteodysplastic primordial dwarfism, type 1, microcephalic osteodysplastic primordial dwarfism, type I.