McCune-Albright syndrome is a genetic disease that causes pigmentation of the skin and also affects the bones. This syndrome is caused by mutations in the GNAS1 gene. A small number of the patient’s cells may contain the faulty gene. This disease does not get inherited i.e. it does not get transferred from the parent to the offspring. It is a rare disease that has been said to have an estimated prevalence between 1/100,000 and 1/1, 000, 000.
In this disease, different areas of the body develop abnormal scar-like tissues in the bones; this condition is called polyostotic fibrous dysplasia. Polyostotic implies that the abnormal areas or lesions may occur in more than one bone and this is often confined to just one side of the body. A replacement of bone that has fibrous tissue may cause uneven growth, fractures and deformity.
As the lesions start in the bones of the skull as well as jaw, it may cause an asymmetric development of the face. Asymmetry may also develop in the long bones and there may be an uneven growth of bones in the legs that can cause limping. There may also be an abnormal curvature of the spine, also called scoliosis. The bone lesions may become cancerous, though this happens in lesser than 1 percent of the people suffering from McCune-Albright syndrome.
Apart from abnormalities in the bone the affected individuals may also light brown patches; these are called café-au-lait spots. These spots may be present right from birth. Just like the bone lesions, café-au-lait spots in McCune-Albright syndrome tend to appear on just one side of the body.
Girls who are born with the syndrome tend to reach puberty earlier than other, healthy girls. They tend to start menstruating by the time they are 2 years old, many years before the secondary sex characters such as breast enlargement and pubic hair are evident. Even boys with the syndrome can have an early puberty. In girls, it is said to start because of an excess of estrogen, a female sex hormone that is produced by cysts developing in one of the ovaries.
A person with McCune-Albright syndrome may also have endocrine problems. They may develop goitre, have hyperthyroidism, etc. These could then lead to fast heart rate, weight loss, high blood pressure, sweating, tremors as well as other symptoms. The pituitary gland which is a structure at the base of the brain can make several hormones and this may produce an excessive amount of growth hormone. A excess of the growth hormone can lead to acromegaly, which is characterised by large feet and hands, distinctive facial features and arthritis.
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