Cartilage-hair hypoplasia is a rare genetic/immunologic disease characterized by disproportionate short stature and immune deficiency. It is genetic because it runs in certain families with identifiable genes. The condition is also an immune-deficiency because there is low, but not absent, T-cell function (the cells that help defend the body from foreign hosts). The low T-cell function makes these children susceptible to specific kinds of infections.
Cartilage-hair hypoplasia principally affects the limbs. Changes are seen in bone formation in an area of long bone (i.e. arm or leg) that connects the end and shaft of the bone called the metaphysis. This leads to the short stature, where the limbs are disproportionately short for the head and torso. The condition also impairs the immune system.
In 1965, an unusual form of disproportionate short stature with frequent and severe infections was reported among the Pennsylvania Amish; some non-Amish, such as Finnish, cases have since been described. The disease arises when the child is missing both gene copies. The condition results from a defective gene that is inherited from each of the parents. Onset of symptoms occurs at infancy. There is equal incidence in both male and female.
Signs and Symptoms
Short and thick hands with redundant (i.e. excess) skin.
Abnormalities of the spine, hyper extensible fingers, and an inability to extend the elbows completely
Very fine, thin hair on the head, eyebrows, and eyelashes (hence, the name).
Decreased immunity, low white blood cell count, low red cell count, and increased rates of malignancy have been described. This puts them at high risk for respiratory infections and severe chickenpox infections.
Cartilage-hair hypoplasia is caused by a defect in a gene. Since the child gets two copies of that gene, one from each parent, both copies must be defective in order to acquire the disease.
Here are a couple of methods clinicians use to diagnose Cartilage hair hypoplasia. First, the blood may be checked to see if there is an absence of T cell function and/or low white blood cell count. Second, the clinician may also use an X-rTay to see if there is a disturbance in the development of cartilage in the long bone of the hand, foot, and knee (also called metaphyseal chondrodysplasia), rib abnormalities, short limb bones with flared ends, or delayed wrist development.
Since the gene has not been currently identified, the fundamental molecular abnormality is unknown. Treatment is supportive, mainly treating infections as they arise and correcting orthopedic problems if they are causing difficulty. There have been two reported cases in which bone marrow transplant has restored the immune system in children who had complete absence of T-cells. Children often get lung infections and should be treated appropriately for those. Although there is no direct cure, there is research concerning immune deficiency disorders.
Those with milder types of immune deficiency have lived to adulthood, some even to old age. Please note, however, the severity of the immunodeficiency varies; in one series, 11 of 77 patients died before age 20 yr but two were still alive at age 76.
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A thorough, somewhat technical summary of the disease.