Mccune-Albright Syndrome (MAS)

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MedlinePlus Genetics: ⁴² McCune-Albright syndrome is a disorder that affects the bones, skin, and several hormone-producing (endocrine) tissues.People with McCune-Albright syndrome develop areas of abnormal scar-like (fibrous) tissue in their bones, a condition called polyostotic fibrous dysplasia. Polyostotic means the abnormal areas (lesions) may occur in many bones; often they are confined to one side of the body. Replacement of bone with fibrous tissue may lead to fractures, uneven growth, and deformity. When lesions occur in the bones of the skull and jaw it can result in uneven (asymmetric) growth of the face. Asymmetry may also occur in the long bones; uneven growth of leg bones may cause limping. Abnormal curvature of the spine (scoliosis) may also occur. Bone lesions may become cancerous, but this happens in fewer than 1 percent of people with McCune-Albright syndrome.In addition to bone abnormalities, affected individuals usually have light brown patches of skin called café-au-lait spots, which may be present from birth. The irregular borders of the café-au-lait spots in McCune-Albright syndrome are often compared to a map of the coast of Maine. By contrast, café-au-lait spots in other disorders have smooth borders, which are compared to the coast of California. Like the bone lesions, the café-au-lait spots in McCune-Albright syndrome may appear on only one side of the body.Girls with McCune-Albright syndrome may reach puberty early. These girls often have menstrual bleeding by age 2. This early onset of menstruation is believed to be caused by excess estrogen, a female sex hormone, produced by cysts that develop in one of the ovaries. Less commonly, boys with McCune-Albright syndrome may also experience early puberty.Other endocrine problems may also occur in people with McCune-Albright syndrome. The thyroid gland, a butterfly-shaped organ at the base of the neck, may become enlarged (a condition called a goiter) or develop masses called nodules. About 50 percent of affected individuals produce excessive amounts of thyroid hormone (hyperthyroidism), resulting in a fast heart rate, high blood pressure, weight loss, tremors, sweating, and other symptoms. The pituitary gland (a structure at the base of the brain that makes several hormones) may produce too much growth hormone. Excess growth hormone can result in acromegaly, a condition characterized by large hands and feet, arthritis, and distinctive facial features that are often described as "coarse." Excess growth hormone secretion may also lead to increased expansion of the fibrous dysplasia in the bones, most visibly in the skull. Rarely, affected individuals develop Cushing syndrome, an excess of the hormone cortisol produced by the adrenal glands, which are small glands located on top of each kidney. Cushing syndrome causes weight gain in the face and upper body, slowed growth in children, fragile skin, fatigue, and other health problems. In people with McCune-Albright syndrome, Cushing syndrome occurs only before age 2.Problems in other organs and systems, such as noncancerous (benign) gastrointestinal growths called polyps and other abnormalities, can also occur in McCune-Albright syndrome.

MalaCards based summary: Mccune-Albright Syndrome, also known as polyostotic fibrous dysplasia, is related to fibrous dysplasia and acth-independent cushing syndrome. An important gene associated with Mccune-Albright Syndrome is GNAS (GNAS Complex Locus), and among its related pathways/superpathways are Metabolism of proteins and ERK Signaling. The drugs Risedronic acid and Etidronic acid have been mentioned in the context of this disorder. Affiliated tissues include bone, skin and thyroid, and related phenotypes are fibrous dysplasia of the bones and precocious puberty

GARD: ¹⁹ McCune-Albright syndrome (MAS) is a disorder that affects the skin, skeleton, and certain endocrine organs (hormone-producing tissues). Cafe-au-lait spots of the skin are common and are usually the first apparent sign of MAS. The main skeletal feature is fibrous dysplasia, which ranges in severity and can cause various complications. Early skeletal symptoms may include limping, pain, or fracture. Endocrinous features may include precocious puberty especially in girls (resulting of estrogen excess from ovarian cysts), excess growth hormone; thyroid lesions with possible hyperthyroidism; renal phosphate wasting, and, rarely, Cushing syndrome caused by an excess of the hormone cortisol produced by the adrenal glands, which are small glands located on top of each kidney. MAS is not inherited. MAS is caused by a somatic genetic change in a gene called GNAS, which is acquired after an egg is fertilized and only affects some of the body's cells and tissues.

OMIM®: ⁵⁷ Activating or gain-of-function GNAS1 mutations in patients with the McCune-Albright syndrome (MAS) are present in the mosaic state, resulting from a postzygotic somatic mutation appearing early in the course of development which yields a monoclonal population of mutated cells within variously affected tissues. The nonmosaic state for most activating mutations is presumably lethal to the embryo. The disorder is characterized clinically by the classic triad of polyostotic fibrous dysplasia (POFD), cafe-au-lait skin pigmentation, and peripheral precocious puberty. However, the disorder is clinically heterogeneous and can include various other endocrinologic anomalies such as thyrotoxicosis, pituitary gigantism, and Cushing syndrome (219080) (Lumbroso et al., 2004). (174800) (Updated 08-Dec-2022)

UniProtKB/Swiss-Prot ⁷³ Mccune-albright syndrome: Characterized by polyostotic fibrous dysplasia, cafe-au-lait lesions, and a variety of endocrine disorders, including precocious puberty, hyperthyroidism, hypercortisolism, growth hormone excess, and hyperprolactinemia. The mutations producing MAS lead to constitutive activation of GS alpha.

Overlap connective tissue disease: Heritable disorder of connective tissue characterized by involvement of the mitral valve, aorta, skeleton, and skin. MASS syndrome is closely resembling both the Marfan syndrome and the Barlow syndrome. However, no dislocation of the lenses or aneurysmal changes occur in the aorta, and the mitral valve prolapse is by no means invariable.

Orphanet ⁵⁸ Mccune-albright syndrome: McCune-Albright syndrome (MAS) is classically defined by the clinical triad of fibrous dysplasia of bone (FD), café-au-lait skin spots, and precocious puberty (PP).

Fibrous dysplasia of bone: A rare, benign, primary bone dysplasia characterized by progressive replacement of normal bone and marrow with fibrous connective tissue in either one (monostotic) or multiple (polyostotic) bones. Clinical manifestations depend on the anatomic location of the replacement and may include bone pain, deformities, pathological fractures, and cranial nerve deficits.

Disease Ontology: ¹¹ A syndrome that is characterized by polyostotic fibrous dysplasia, precocious puberty, and café-au-lait spots and has material basis in spontaneous post zygotic missense mutation at ARG201 or Gln227 of the GNAS gene during embryogenesis.

Wikipedia ⁷⁵ Mccune-albright syndrome: McCune-Albright syndrome is a complex genetic disorder affecting the bone, skin and endocrine systems.... more...

Fibrous dysplasia of bone: Fibrous dysplasia is a disorder where normal bone and marrow is replaced with fibrous tissue, resulting... more...

Mass syndrome: MASS syndrome is a medical disorder of the connective tissue similar to Marfan syndrome. MASS stands... more...

Clinical features from OMIM®:

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