Short-rib thoracic dysplasia 9 is a recently reported hereditary syndrome with major manifestations in the kidney, skeletal, liver, and ocular systems.
Infants are usually born with a shortened thorax (rib cage) and actual shortened ribs that may be severe enough to cause breathing problems. The body length at birth is unknown but shortness of stature is apparent later. The long bones of the limbs are somewhat short as well. The fingers and toes appear short as a result of abnormal (cone-shaped) growth plates called epiphyses and this may affect the head of the large leg bone known as the femur as well.
The liver may be enlarged but later becomes scarred (fibrotic). The kidneys are often cystic and some malfunction is often evident in the first decade of life. The kidney disease is progressive and often defines the duration of survival as complete failure can occur.
The eye findings have not been fully defined but it seems that difficulty seeing in dim light is an early symptom. There is also loss of vision as a result of degenerative disease in the retina is progressive as well. At least one patient has retained functional vision at the age of 40 years.
This condition is the result of mutations in both members of a pair of genes and is therefore follows an autosomal recessive pattern of inheritance. Most parents (who carry only one copy of the mutation) are clinically normal but the offspring of two such parents convey a 25% risk for short-rib thoracic dysplasia 9 to each of their children.
This is a rare condition and difficult to diagnose. The misshapen chest may provide a clue, especially when breathing problems are associated. The shortened length of the newborn, while nondescript, is helpful in association with the deformed chest. Other features such as the liver, kidney, and eye disease may not be apparent until later in the first decade of life.
The complex, multifaceted nature of this condition requires constant monitoring. Kidney dysfunction is progressive and must be periodically evaluated since total failure can occur. The progression of the kidney disease often defines the length of survival for children but some patients have benefitted from kidney transplantation. There is no treatment for the retinal deterioration but specially tinted lenses and low vision aids, especially for school age children can be helpful.