SNP Shot: Genomic Insights

Multiple epiphyseal dysplasia (MED) is a condition affecting cartilage and bone growth, primarily at the ends of the long bones (epiphyses) in the arms and legs. There are two forms of MED, categorized by their inheritance pattern. Both dominant and recessive MED share relatively mild symptoms such as joint pain, commonly in the hips and knees, early arthritis, and a distinctive waddling gait. While some individuals with MED may experience mild short stature in adulthood, most reach a normal adult height. Diagnosis typically occurs during childhood, although milder cases may go undetected until adulthood.

Recessive MED differs from the dominant form by the presence of deformities in the hands, feet, and knees, along with scoliosis (abnormal spinal curvature). Approximately half of individuals with recessive MED are born with at least one unusual feature. These can include clubfoot (a foot that turns inward and upward), cleft palate (an opening in the roof of the mouth), clinodactyly (unusual curvature of the fingers or toes), or swelling of the ears. A double-layered patella, an abnormality of the kneecap, is also relatively common in this form of MED.

Inheritance:

MED can be passed down through families in different ways. Autosomal dominant inheritance occurs when only one copy of a mutated gene is needed to cause the condition. Individuals with dominant MED may inherit the mutation from an affected parent, or the mutation may arise spontaneously in their genes, even if there is no family history of the disorder. MED can also follow an autosomal recessive inheritance pattern. In this case, both copies of a gene must be mutated for the condition to manifest. Typically, the parents of a child with autosomal recessive MED each carry one copy of the mutated gene, but they themselves do not exhibit any signs or symptoms of the condition.