SNP Shot: Genomic Insights

Hypochondroplasia is a type of dwarfism characterized by shortened limbs. It disrupts ossification, the process where cartilage turns into bone, especially in the long bones of the arms and legs. While similar to achondroplasia, another skeletal condition, hypochondroplasia generally presents with milder features.

Short stature is a universal characteristic of hypochondroplasia. In men, adult height typically ranges from 138 to 165 centimeters (4'6" to 5'5"). Women with the condition usually reach an adult height between 128 and 151 centimeters (4'2" to 4'11").

Individuals with hypochondroplasia have disproportionately short arms and legs, along with wide, short hands and feet. Other common features include an enlarged head (macrocephaly), restricted elbow movement, an accentuated curve in the lower back (lordosis), and bowed legs. These characteristics are usually less severe compared to those seen in achondroplasia and may become apparent later, during early to middle childhood. There is a slightly elevated risk of temporal lobe epilepsy, a seizure disorder. While some research suggests a small number of individuals with hypochondroplasia may experience mild to moderate intellectual disability or learning difficulties, other studies have shown inconsistent results.

Inheritance:

Hypochondroplasia follows an autosomal dominant inheritance pattern. This means that only one copy of a mutated gene in each cell is enough to cause the condition. Most individuals with hypochondroplasia are born to parents of average height who do not have the condition themselves. These cases arise from new mutations in the FGFR3 gene. In other instances, people with hypochondroplasia inherit a mutated FGFR3 gene from one or both parents affected by the condition. Individuals who inherit two mutated copies of the FGFR3 gene tend to experience more severe bone growth problems compared to those who inherit only one copy.