SNP Shot: Genomic Insights

Rhizomelic chondrodysplasia punctata (RCDP) is a rare genetic disorder that disrupts normal development, impacting many parts of the body. Key characteristics include skeletal abnormalities, distinctive facial features, intellectual disability, and breathing difficulties.

RCDP is defined by rhizomelia, or shortening of the upper arm and thigh bones. Individuals with RCDP also exhibit chondrodysplasia punctata, a specific bone abnormality detectable on x-rays, which affects long bone growth. Joint contractures, causing stiffness and pain, are also common.

Characteristic facial features in RCDP include a prominent forehead, widely spaced eyes (hypertelorism), a sunken midface (midface hypoplasia), a small nose with upturned nostrils, and full cheeks. Congenital or early-onset cataracts (clouding of the eye lenses) are nearly universal in affected individuals.

RCDP is linked to significant developmental delays and severe intellectual disability. Most children with RCDP struggle to reach typical milestones like sitting unsupported, self-feeding, or speaking in phrases. Infants with RCDP experience significantly slower growth rates and are prone to seizures. Frequent respiratory infections and life-threatening respiratory problems are common. Due to the severity of these health challenges, most individuals with RCDP do not survive past childhood, rarely living beyond the age of 10. However, some individuals with milder forms of the condition have survived into early adulthood.

There are three identified types of RCDP: type 1 (RCDP1), type 2 (RCDP2), and type 3 (RCDP3). These types share similar characteristics and are differentiated by their underlying genetic causes.

Inheritance:

RCDP follows an autosomal recessive inheritance pattern. This means that both copies of the relevant gene in each cell must have mutations for the condition to manifest. Parents of an individual with RCDP each carry one copy of the mutated gene but usually do not exhibit any signs or symptoms of the disorder.