Spondyloepimetaphyseal dysplasia X-linked (SEMDX) is a rare condition that begins in early childhood. Someone with SEMDX will not appear to have symptoms of the condition at birth, but will start to as they grow. Someone with SEMDX will be shorter than most other people. SEMDX will also cause the hands and feet to be short.
SEMDX will cause bone growth problems in the vertebrae, femurs, pelvis, ulnas, and fibulas. The vertebrae, femur, pelvis, ulna, and fibula are all bones in the body. The vertebrae are the bones that make up the spine (the group of bones that run down a person’s back). SEMDX will cause the vertebrae to be flat. The femurs are the large bones in the thighs. The pelvis is the large bone that makes up the hips. SEMDX will cause the pelvis to be narrow. The ulna is a bone in the lower arm. The fibula is a bone in the lower leg.
SEMDX is passed down from parents to their children through genes. Genes are sections of DNA that act as the body’s instruction manual. DNA is wound up tightly into structures called chromosomes. Males have an X and a Y chromosome. The X chromosome comes from their mother, and the Y chromosome comes from their father. Females have two X chromosomes, one from each parent.
SEMDX is inherited in an X-linked recessive pattern. This means that a female needs both of her X chromosomes to have the mutated (changed) SEMDX gene in order to have SEMDX. Females who have one X chromosome with the mutated SEMDX gene will not have the disease. However, they can pass the SEMDX gene down to their children. Because males only have one X chromosome, they will have SEMDX if their X chromosome has the mutated SEMDX gene. If you or a family member has been diagnosed with SEMDX, talk to your doctor about the most current treatment options. Support groups are also good sources of support and information.