McCune–Albright syndrome

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McCune-Albright syndrome
Mccune-albrightsyndrome1.jpg
Café-au-lait skin pigmentation.
A) A typical lesion on the face, chest, and arm of a 5-year-old girl with McCune-Albright syndrome which demonstrates jagged "coast of Maine" borders, and the tendency for the lesions to both respect the midline and follow the developmental lines of Blaschko.
B) Typical lesions that are often found on the nape of the neck and crease of the buttocks are shown (arrows).
Specialty Medical genetics Edit this on Wikidata

McCune–Albright syndrome is a complex genetic disorder affecting the bone, skin, and endocrine systems. It is a mosaic disease arising from somatic activating mutations in GNAS, which encodes the alpha-subunit of the Gs G-coupled protein receptor. These mutations lead to constitutive receptor activation.[1]

It was first described in 1937 by Donovan James McCune and Fuller Albright.[2][3][4]

Signs and symptoms[edit]

McCune–Albright syndrome is suspected when two or more of the following features are present:

Patients may have one or many of these features, which may occur in any combination. As such, the clinical presentation of patients with McCune Albright Syndrome varies greatly depending on the disease features.

Various endocrine diseases may present in McCune–Albright syndrome due to increased hormone production.

  • Precocious puberty: The most common endocrinopathy is precocious puberty, which presents in girls (~85%) with recurrent estrogen-producing cysts leading to episodic breast development, growth acceleration, and vaginal bleeding.[5][6] Precocious puberty may also occur in boys with McCune–Albright syndrome, but is much less common (~10-15%).[6]
  • Testicular abnormalities: Testicular abnormalities are seen in a majority (~85%) of boys with McCune-Albright Syndrome.[6][7][8]
  • Hyperthyroidism: Hyperthyroidism occurs in approximately one-third of patients with McCune Albright Syndrome. Many others may suffer from other kinds of thyroid involvement.[6][7][8]
  • Growth Hormone Excess: GNAS mutation in the anterior pituitary can result in excess growth hormone secretion and is found in approximately 10-15% of patients.[6]
  • Cushing's Syndrome: In McCune-Albright Syndrome, Cushing's syndrome is a very rare feature that develops only in infancy.[9]

Genetics[edit]

Genetically, there is a spontaneous postzygotic mutation of the gene GNAS, on the long (q) arm of chromosome 20 at position 13.3, which is involved in G-protein signaling.[10] This mutation, which occurs only in the mosaic state, leads to constitutive receptor signaling and inappropriate production of excess cAMP.

The mutation that causes McCune–Albright syndrome arises very early during embryogenesis. Because all cases of the syndrome are sporadic, it is believed that the mutation would be lethal if it affected all cells in the embryo. Mutant cells can only survive when they are intermixed with normal cells.[11]

There are no known risk factors for acquiring McCune–Albright syndrome, and no exposures during pregnancy that are known to either cause or prevent the mutation from occurring. The disease cannot be inherited and occurs equally among all ethnic groups.[12]

Diagnosis and Treatment[edit]

McCune–Albright syndrome has different levels of severity. For example, one child with McCune–Albright syndrome may be entirely healthy, with no outward evidence of bone or endocrine problems, enter puberty at close to the normal age, and have no unusual skin pigmentation. Diagnosis may be made only after decades. In other cases, children are diagnosed in early infancy, show obvious bone disease, and obvious increased endocrine secretions from several glands.

Treatment is dictated by both the tissues affected and the extent to which they are affected.[12]

Skeletal abnormalities[edit]

Patients with fibrous dysplasia may have bone fractures, pain, and deformities. Patients may also develop low blood phosphate levels due to overproduction of the protein fibroblast growth factor 23.[13]

CT scan of the skull is the most useful test for craniofacial fibrous dysplasia. Regular hearing and vision screening is recommended. X-rays are usually sufficient to reveal fibrous dysplasia of the appendicular skeleton, but CT and/or MRI scans can reveal microfractures. Regular screening for scoliosis should also be undertaken.

Surgical management of skeletal abnormalities has evolved over the years. Surgical intervention may be necessary for some skeletal abnormalities. Bisphosphonates are helpful in relieving bone pain, but it is no longer believed that they prevent progression of the disease. Muscle strengthening exercises are important for preventing bone fractures; cycling and swimming are recommended in order to reduce the risk of fracture during exercise. [12]

Endocrine abnormalities[edit]

Precocious puberty is more common in females, but may occur in males as well. Drugs such as letrozole and anastrozole can be used to prevent short stature in both males and females. In males, drugs such as spironolactone and flutamide can be used to treat the behavioral issues associated with androgen excess.

Males with McCune-Albright syndrome may present with benign testicular tumors, though testicular cancer appears to be rare. Annual ultrasounds of testicular masses should be performed to screen for cancer.

Hyperthyroidism is found in about 38% of patients. Medications such as thioamides are useful in treating these symptoms. However, as thyroid symptoms in this disorder almost never resolve spontaneously, surgery or radiation are more definitive treatments. Annual thyroid ultrasounds should be performed to screen for thyroid cancer. Hyperparathyroidism secondary to Vitamin D deficiency is common, and may worsen fibrous dysplasia. Levels of calcium and parathyroid hormone should be periodically assessed.

In one study, 18% of McCune-Albright patients had hypophosphatemia due to kidney involvement. High doses of oral phosphate and calcitriol should be given for treatment.

Pituitary hormone abnormalities may occur. Growth hormone excess may worsen craniofacial dysplasia; treatment with somatostatin analogues or pegvisomant may be effective. Surgery may be an option, but may be complicated by the cranial abnormalities associated with the disorder. Excessive prolactin secretion may also occur; this is treated with dopamine agonists such as cabergoline.

Cushing syndrome is a rare but potentially fatal complication that can occur in the first year of life. Adrenalectomy is the treatment of choice. Metyrapone may also be used for treatment.[12]

Epidemiology[edit]

McCune-Albright Syndrome is estimated to occur at a frequency between 1 person in 100,000 to 1 person in 1,000,000 individuals worldwide.[14]

Notable cases[edit]

Mauricio Saravia, an Uruguayan artist with the disease

Lauren Ruotolo is an author and involved in advocacy for McCune–Albright syndrome [15]

Mauricio Saravia is an artist and graphic designer [16]

See also[edit]

References[edit]

  1. ^ Boyce, Alison M.; Collins, Michael T. (1993). Adam, Margaret P.; Ardinger, Holly H.; Pagon, Roberta A.; Wallace, Stephanie E.; Bean, Lora JH; Mefford, Heather C.; Stephens, Karen; Amemiya, Anne; Ledbetter, Nikki, eds. GeneReviews(®). Seattle (WA): University of Washington, Seattle. PMID 25719192. 
  2. ^ synd/1844 at Who Named It?
  3. ^ McCune, Donovan J.; Bruch, Hilde (1937). "Progress in Pediatrics: Osteodystrophia Fibrosa". Archives of Pediatrics & Adolescent Medicine. 54 (4): 806. doi:10.1001/archpedi.1937.01980040110009. 
  4. ^ Albright F, Butler AM, Hampton AO, Smith P (1937). "Syndrome characterized by osteitis fibrosa disseminata, areas of pigmentation and endocrine dysfunction, with precocious puberty in females: report of five cases". N. Engl. J. Med. 216 (17): 727–746. doi:10.1056/NEJM193704292161701. 
  5. ^ Estrada, Andrea; Boyce, Alison M.; Brillante, Beth A.; Guthrie, Lori C.; Gafni, Rachel I.; Collins, Michael T. (November 2016). "Long-term Outcomes of Letrozole Treatment for Precocious Puberty in Girls with McCune-Albright Syndrome". European journal of endocrinology. 175 (5): 477–483. doi:10.1530/EJE-16-0526. ISSN 0804-4643. PMC 5066167Freely accessible. PMID 27562402. 
  6. ^ a b c d e Boyce, Alison M; Collins, Michael T. "Fibrous Dysplasia/McCune-Albright Syndrome Gene Reviews". NCBI Books. Retrieved 6 January 2018. 
  7. ^ a b Celi, Francesco S.; Coppotelli, Giuseppe; Chidakel, Aaron; Kelly, Marilyn; Brillante, Beth A.; Shawker, Thomas; Cherman, Natasha; Feuillan, Penelope P.; Collins, Michael T. (June 2008). "The Role of Type 1 and Type 2 5′-Deiodinase in the Pathophysiology of the 3,5,3′-Triiodothyronine Toxicosis of McCune-Albright Syndrome". The Journal of Clinical Endocrinology and Metabolism. 93 (6): 2383–2389. doi:10.1210/jc.2007-2237. ISSN 0021-972X. PMC 2435649Freely accessible. PMID 18349068. 
  8. ^ a b Salenave, Sylvie; Boyce, Alison M.; Collins, Michael T.; Chanson, Philippe (June 2014). "Acromegaly and McCune-Albright Syndrome". The Journal of Clinical Endocrinology and Metabolism. 99 (6): 1955–1969. doi:10.1210/jc.2013-3826. ISSN 0021-972X. PMC 4037730Freely accessible. PMID 24517150. 
  9. ^ Brown, Rebecca J.; Kelly, Marilyn H.; Collins, Michael T. (April 2010). "Cushing Syndrome in the McCune-Albright Syndrome". The Journal of Clinical Endocrinology and Metabolism. 95 (4): 1508–1515. doi:10.1210/jc.2009-2321. ISSN 0021-972X. PMC 2853983Freely accessible. PMID 20157193. 
  10. ^ Collins MT, Sarlis NJ, Merino MJ, et al. (September 2003). "Thyroid carcinoma in the McCune-Albright syndrome: contributory role of activating Gs alpha mutations". J. Clin. Endocrinol. Metab. 88 (9): 4413–7. doi:10.1210/jc.2002-021642. PMID 12970318. 
  11. ^ Happle, R. (1986). "The McCune-Alrbight syndrome: a lethal gene surviving by mosaicism". Clinical Genetics. 29: 321–324. doi:10.1111/j.1399-0004.1986.tb01261.x. 
  12. ^ a b c d Dumitrescu, Claudia E.; Collins, Michael T. (19 May 2008). "McCune-Albright syndrome". Orphanet Journal of Rare Diseases. 3 (1): 1. doi:10.1186/1750-1172-3-12. 
  13. ^ Riminucci, Mara; Collins, Michael T.; Fedarko, Neal S.; Cherman, Natasha; Corsi, Alessandro; White, Kenneth E.; Waguespack, Steven; Gupta, Anurag; Hannon, Tamara (2003-09-01). "FGF-23 in fibrous dysplasia of bone and its relationship to renal phosphate wasting". Journal of Clinical Investigation. 112 (5): 683–692. doi:10.1172/JCI18399. ISSN 0021-9738. PMC 182207Freely accessible. PMID 12952917. 
  14. ^ NIH Library https://ghr.nlm.nih.gov/condition/mccune-albright-syndrome. Retrieved 6 January 2018.  Missing or empty |title= (help)
  15. ^ "Home". Lauren Ruotolo. Retrieved 2017-11-25. 
  16. ^ "Mauricio Saravia :: Bio". www.mauriciosaravia.com. Retrieved 2017-11-25. 

External links[edit]

Classification
External resources