Microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1) is a genetic condition that is mainly characterized by intrauterine and post-natal growth retardation; an abnormally small head size (microcephaly); abnormal bone growth (skeletal dysplasia); distinctive facial features; and brain anomalies. Other signs and symptoms include sparse hair and eyebrows; dry skin; short limbs; dislocation of the hips and elbows; seizures; and intellectual disability. It is caused by mutations in the RNU4ATAC gene and is inherited in an autosomal recessive manner. Treatment is supportive only. The prognosis is poor with most affected individuals dying within the first year of life. MOPD types 1 and 3 were originally thought to be separate entities, but more recent reports have confirmed that the two forms are part of the same syndrome.

Microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1) has been shown to be caused by mutations in the RNU4ATAC gene.

Individuals with MOPD1 may have low birth weight, growth retardation, short limbs, broad hands, small head size (microcephaly), abnormal bone growth (skeletal dysplasia) and a distinct facial appearance. Facial characteristics may include a sloping forehead; protruding eyes; prominent nose with a flat nasal bridge; and small jaw (micrognathia). In addition, babies with MOPD1 may experience short episodes of stopped breathing (apnea) and seizures. Affected individuals also commonly have sparse hair and eyebrows; dry skin; dislocation of the hips or elbows; and intellectual disability. Brain abnormalities that have been reported include lissencephaly, hypoplastic (underdeveloped) frontal lobes, and agenesis of the corpus callosum or cerebellar vermis (the nerve tissue that connects the two halves of the cerebellum).

MOPD1 is thought to be inherited in an autosomal recessive manner. This means that affected individuals have abnormal gene changes (mutations) in both copies of the disease-causing gene, with one copy inherited from each parent. The parents who each carry one abnormal copy of the gene are referred to as carriers; carriers typically do not show signs or symptoms of an autosomal recessive condition. When two carriers have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.

At this time there are no specific treatments for MOPD1. Treatment is generally supportive. The prognosis is poor for affected individuals, with most of the reported patients dying within the first year of life.

Prognosis can vary from patient to patient, however it is generally poor. Some babies are stillborn. Most infants pass away with in a year, often due to infectious diseases.