SNP Shot: Genomic Insights

Microcephalic osteodysplastic primordial dwarfism type II (MOPDII) is a rare disorder marked by dwarfism (short stature), bone abnormalities (osteodysplasia), and an unusually small head (microcephaly). Growth deficiencies begin before birth (primordial dwarfism), with babies experiencing slow prenatal growth (intrauterine growth retardation). This slow growth continues after birth, resulting in final adult heights between 20 and 40 inches. Skeletal issues in MOPDII can include hip dysplasia, thinning of arm and leg bones, scoliosis (an abnormal spinal curvature), and shortened wrist bones. While head growth slows significantly, resulting in an adult brain size comparable to a 3-month-old, intellectual development is usually normal.

Individuals with MOPDII often have a high-pitched, nasal voice and, in some cases, a narrowing of the voicebox (subglottic stenosis). Distinctive facial features include a prominent nose, full cheeks, a long midface, and a small jaw. Other possible signs and symptoms are small teeth (microdontia) and farsightedness. Changes in skin pigmentation, with light or dark patches, may appear over time.

Many individuals with MOPDII have abnormalities in their blood vessels. Some may develop an intracranial aneurysm, a bulge in a blood vessel in the brain. This poses a risk of rupture and brain hemorrhage. Others may have Moyamoya disease, characterized by narrowed arteries at the base of the brain, restricting blood flow. While often treatable, these vascular issues increase the risk of stroke and can shorten lifespan.

Inheritance:

MOPDII follows an autosomal recessive inheritance pattern. This means that both copies of the gene in each cell must have mutations for the condition to manifest. Individuals with MOPDII inherit one mutated copy from each parent, who typically do not exhibit symptoms of the condition themselves.