McCune-Albright Syndrome (MAS)
Description
McCune-Albright Syndrome (MAS) is a rare genetic disorder characterized by a distinctive triad of symptoms: fibrous dysplasia of bone, café-au-lait spots (light brown skin patches), and endocrine dysfunction. This syndrome typically affects girls more frequently than boys and often presents in early childhood. Understanding the causes, symptoms, and management of MAS is crucial for providing optimal care to those affected.
Genes Involved
Genes Involved:
MAS is caused by a mutation in the GNAS gene. This gene provides instructions for making a protein called the stimulatory G protein alpha subunit (Gsα). This protein plays a role in regulating various cell functions, including hormone production.
The mutation in the GNAS gene leads to overactivity of the Gsα protein in specific tissues, resulting in the characteristic features of MAS.
Recognizing the Signs and Symptoms
Recognizing the Signs and Symptoms:
- Fibrous Dysplasia of Bone: Abnormal bone development leading to fragile and misshapen bones. Fractures can occur easily.
- Café-au-lait Spots: Light brown, irregularly shaped skin patches present at birth or developing later. These spots are often larger than those found in other conditions like neurofibromatosis.
- Endocrine Dysfunction: Abnormal hormone production from various glands, leading to conditions like precocious puberty, hyperthyroidism, or Cushing‘s syndrome. The affected gland and associated symptoms vary.
Other symptoms that can occur with MAS include:
- Vision problems: Due to abnormalities in the eye bones.
- Hearing loss: Caused by bone abnormalities affecting the ear.
- Growth problems: Short stature or uneven growth.
- Heart problems: Abnormal development of the heart valves.
- Mental retardation: In some cases, but not always.
Causes
Causes:
MAS is caused by a mutation in the GNAS gene, which is inherited in a sporadic (non-inherited) manner. This means that the mutation occurs spontaneously in a single cell during early embryonic development. The mutation is not passed down from parents, and there is no family history of the syndrome.
This mutation affects the GNAS gene in a specific way, leading to overactivity of the Gsα protein in some cells but not others. This explains why the symptoms of MAS are variable and affect different tissues in different people.
Inheritance/recurrence risk
Inheritance or Recurrence Risk:
MAS is not an inherited condition. The mutation occurs sporadically, meaning it is not passed down from parents. The risk of a parent having another child with MAS is extremely low.
However, if a person with MAS has children, there is a 50% chance of passing the GNAS gene mutation to their offspring. This does not mean that their children will have MAS. The child‘s chance of developing MAS depends on various factors, including the specific mutation, its location within the GNAS gene, and the tissue affected.
