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Characterized by the triad of polyostotic fibrous dysplasia, café-au-lait skin pigmentation, and autonomous endocrine hyperfunction. The most common form of autonomous endocrine hyperfunction is gonadotropin-independent precocious puberty, but affected individuals also may have hyperthyroidism, hypercorticism, pituitary gigantism, or acromegaly. Nonendocrine abnormalities in this disorder include hypophosphatemia, chronic liver disease, tachycardia, and rarely sudden death, possibly from cardiac arrhythmias.

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McCune-Albright syndrome
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Cushing-like habitus and café-au-lait skin pigmentation in a small girl with McCune-Albright syndrome. Note precocious breast development.

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Polyostotic Fibrous Dysplasia; Osteitis Fibrosa Cystica; McCune Syndrome; Albright Syndrome; Osteitis Fibrosa Disseminata.

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Genetic disorder first described in 1936 by Donovan James McCune, an American pediatrician, and then in 1937 by Fuller Albright, an American physician.

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Occurs sporadically; more common in females.

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Autosomal dominant lethal mosaic postzygotic somatic mutation in the GNAS 1 gene located on chromosome 20q13.2.

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Described as a mosaicism for a mutation in the gene encoding the subunit of the G protein stimulating cyclic adenosine monophosphate (cAMP) formation. This results in activation of various cAMP-dependent receptors including adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) receptors leading to autonomous and aberrant behavior toward otherwise normal stimuli.

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Classic triad of endocrine dysfunction, bone lesions, and pigmented skin lesions. Average age of onset is 3 years. Precocious pseudopuberty (F > M); vaginal bleeding may begin as early as age 4 months and secondary sexual characteristics as early as 6 months. Acromegaly (F = M). Cushing syndrome may occur in early infancy before onset of precocious pseudopuberty and is associated with adrenocortical hyperplasia. Multinodular goiter (M = F) and hyperthyroidism in 20 to 40% of patients. Pathologic fractures and deformities of long bones resulting from hypophosphatemic osteomalacia. Shepherd crook deformity of the proximal femur is particularly characteristic, and bony lesions in the base of skull may result in cranial nerve compression, blindness, and deafness. Large, patchy cutaneous pigmentation with irregular margins on neck, face, back, and shoulders are found in approximately 90% of children with this syndrome. Both the bony and skin lesions are limited predominantly to one side.

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Clinical features of endocrine abnormalities, café-au-lait spots, and polyostotic fibrous dysplasia. Biochemical: Thyroid (mildly elevated T3, low TSH); adrenal (raised cortisol and low ACTH levels, adrenal function not suppressed by dexamethasone); pituitary (elevated growth hormone and prolactin levels); hypophosphatemia as a result of decreased resorption of phosphate in the renal tubule; ovaries (estradiol varies from normal to markedly elevated levels, suppressed levels of LH and FSH, no response to luteinizing hormone-releasing hormone stimulation). Imaging studies: Ultrasonography (ovarian cysts, nodular adrenal hyperplasia); skeletal radiography (widespread cystic bony lesions, advanced bone age, fractures and deformities of long bones, bony lesions in base of skull).

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Direct laryngoscopy and tracheal ...

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