Sulfate transporter-related osteochondrodysplasias are a group of diseases impacting how the body makes cartilage and bones. These diseases include achondrogenesis type Ib (ACGIB), diastrophic dysplasia, atelosteogenesis type II, and recessive multiple epiphyseal dysplasia (rMED).
ACGIB is a severe skeletal disease that is fatal either before or shortly after birth. Babies born with this disease have extremely short arms, legs, fingers, and toes. The fingers and toes may be turned inward (clubfoot). These babies also tend to have flat faces, sticking-out abdomens, narrow chests, and short necks with thickening of the soft tissue. Many are born with hernias. Babies with ACGIB are often in the breech position, “upside-down,” with their feet toward the birth canal. Mothers of these babies may have other pregnancy complications, like having too much amniotic fluid.
Diastrophic dysplasia, also called diastrophic dwarfism, causes bone and joint abnormalities. It does not typically affect intellectual abilities. People with diastrophic dysplasia have very short arms and legs, but their skulls are often a normal size. They are often born with bone deformities like clubfoot, cleft palate, a curved spine, and “hitchhiker thumbs” (thumbs that bend back). The outside of the ears may be swollen at birth, leading to abnormal-looking ears later in life. Babies may also have a small ribcage and chest with a sticking-out abdomen, which can cause breathing problems. Joint abnormalities leading to pain develop early, and many have trouble moving their joints, making walking difficult. Atelosteogenesis type II is similar to diastrophic dysplasia, with main symptoms including bone deformities, cleft palate, narrow chest with a sticking-out abdomen, and unusual facial features. The main difference is that atelosteogenesis type II is much more severe, with most affected individuals being stillborn or dying from respiratory failure soon after birth.
rMED causes bone deformities and joint pain. Unlike the other diseases mentioned, individuals with rMED usually reach normal height and live normal lifespans. Half of those with rMED are born with obvious bone abnormalities like cleft palate, clubfoot, or an inwardly-curved little finger. Some also have mild curvature of the spine (scoliosis). Everyone with the disease develops joint pain, often later in childhood. Pain is common in the hips and knees but can also occur in the wrists, fingers, and elsewhere.
This group of conditions is caused by pathogenic (disease-causing) variants in the SLC26A2 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 220 chance to be a carrier.