McCune-Albright syndrome

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Dushka Riaz, MD

Overview

McCune-Albright syndrome is a rare genetic disorder caused by an activating mutation of the GNAS gene resulting in various phenotypic presentations. McCune-Albright syndrome typically presents with the triad of fibrous dysplasia, precocious puberty and café au lait spots in both genders. Other manifestations include acromegaly, Cushing’s syndrome and thyroid hyperplasia or toxic nodular goiters.

Historical Perspective

Classification

There is no established system for the classification of McCune-Albright syndrome.

Pathophysiology

Causes

McCune-Albright syndrome is caused by a missense mutation of the GNAS gene alpha subunit which becomes constitutively activated. This increases intracellular cAMP which activates downstream hormones resulting in multiple tissue types being affected and mosaicism presented in its patients. [2]

Differentiating McCune-Albright syndrome from other Diseases

McCune-Albright syndrome must be differentiated from Neurofibromatosis, isolated fibrous dysplasia and other causes of precocious puberty.

Epidemiology and Demographics

Prevalence

  • The prevalence of McCune-Albright syndrome is between 1:100,000 and 1:1,000,000 making it very rare. [6]

Age

  • McCune-Albright syndrome is more commonly observed among infants and young children. [6]

Gender

  • Girls are more commonly affected with McCune-Albright syndrome than boys. [6]

Race

  • There is no racial predilection for McCune-Albright syndrome. [6]

Risk Factors

There are no risk factors for McCune-Albright syndrome.

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Criteria

  • The diagnosis of McCune-Albright syndrome is a clinical diagnosis. [2]
  • Though there are genetic tests available for the GNAS gene mutation with new PCR techniques for those who show clinical signs of the syndrome. [8]
  • Patients who present with monostotic fibrous dysplasia are required to have evidence of the pathogenic GNAS gene by molecular testing. [3]

Symptoms

Café au lait spot

Physical Examination

Laboratory Findings

Electrocardiogram

There are no ECG findings associated with McCune-Albright syndrome.

X-ray

The fibrous dysplasia of bone is present at multiple sites (polyostotic) and xrays would give a ground glass appearance. [8]

Echocardiography or Ultrasound

US in boys may be helpful in the diagnosis of McCune-Albright syndrome. Findings on an US suggestive of McCune-Albright syndrome include testicular ultrasounds to detect hormonally active tumors.[2]

CT scan

CT scan may be helpful in the diagnosis of McCune-Albright syndrome. Findings on CT scan suggestive of/diagnostic of McCune-Albright syndrome include fibroblastic lesions. It is helpful to identify these early in children to prevent permanent deformities. [2]

MRI

There are no MRI findings associated with McCune-Albright syndrome.

Other Imaging Findings

There are no other imaging findings associated with McCune-Albright syndrome.

Other Diagnostic Studies

  • McCune Albright may be diagnosed using total body bone scintigraphy to identify the fibrous dysplastic lesions. This should then be followed up with radiographs and CT to clearly determine the extent of the lesions.
  • It is helpful to perform baseline ophthalmic and audiologic testing for those patients whose fibrous dysplastic lesions involve the craniofacial area. [3]

Treatment

Medical Therapy

Surgery

  • Surgery should be used in extreme caution for female patients with ovarian cysts because of the high risk of recurrence and resultant decrease in ovarian reserve.
  • Patients with hyperthyroidism are preferred to have a thyroidectomy with total gland resection. [3]

Prevention

  • Once diagnosed, patients with McCune-Albright syndrome are followed-up with:
    • Females – early breast cancer screening.
    • Males – testicular lesions by physical examination and US. [3]
    • Both genders – signs of precocious puberty, growth hormone excess or growth acceleration (IGF-1 levels), monitoring thyroid function (TSH, free T4, and T3), routine radiographs for fibrous dysplasia lesions particularly to check for scoliosis, serum phosphorous to monitor for development of hypophosphatemia [3] and annual vision and hearing testing to monitor fibrotic lesions affecting these areas. [2]
  • Parents should be counseled that McCune-Albright syndrome is not inherited. [3]
  • There is an increased risk for malignancies. [15]
  • Patients should also be advised to avoid contact sports and optic nerve decompressions. [3]

References

  1. Manring MM, Calhoun JH (2011). "Biographical sketch: Fuller Albright, MD 1900-1969". Clin Orthop Relat Res. 469 (8): 2092–5. doi:10.1007/s11999-011-1831-0. PMC 3126964. PMID 21384213.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 "StatPearls". 2020. PMID 30725777.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K; et al. (1993). "GeneReviews®". PMID 25719192.
  4. 4.0 4.1 Javaid MK, Boyce A, Appelman-Dijkstra N, Ong J, Defabianis P, Offiah A; et al. (2019). "Best practice management guidelines for fibrous dysplasia/McCune-Albright syndrome: a consensus statement from the FD/MAS international consortium". Orphanet J Rare Dis. 14 (1): 139. doi:10.1186/s13023-019-1102-9. PMC 6567644 Check |pmc= value (help). PMID 31196103.
  5. DeBella K, Szudek J, Friedman JM (2000). "Use of the national institutes of health criteria for diagnosis of neurofibromatosis 1 in children". Pediatrics. 105 (3 Pt 1): 608–14. doi:10.1542/peds.105.3.608. PMID 10699117.
  6. 6.0 6.1 6.2 6.3 Lumbroso S, Paris F, Sultan C, European Collaborative Study (2004). "Activating Gsalpha mutations: analysis of 113 patients with signs of McCune-Albright syndrome--a European Collaborative Study". J Clin Endocrinol Metab. 89 (5): 2107–13. doi:10.1210/jc.2003-031225. PMID 15126527.
  7. 7.0 7.1 Spencer T, Pan KS, Collins MT, Boyce AM (2019). "The Clinical Spectrum of McCune-Albright Syndrome and Its Management". Horm Res Paediatr. 92 (6): 347–356. doi:10.1159/000504802. PMC 7302983 Check |pmc= value (help). PMID 31865341.
  8. 8.0 8.1 8.2 8.3 8.4 Pratt VM, McLeod HL, Rubinstein WS, Scott SA, Dean LC, Kattman BL; et al. (2012). "Medical Genetics Summaries". PMID 28520344.
  9. de Sanctis C, Lala R, Matarazzo P, Balsamo A, Bergamaschi R, Cappa M; et al. (1999). "McCune-Albright syndrome: a longitudinal clinical study of 32 patients". J Pediatr Endocrinol Metab. 12 (6): 817–26. doi:10.1515/jpem.1999.12.6.817. PMID 10614538.
  10. Frisch LS, Copeland KC, Boepple PA (1992). "Recurrent ovarian cysts in childhood: diagnosis of McCune-Albright syndrome by bone scan". Pediatrics. 90 (1 Pt 1): 102–4. PMID 1614755.
  11. Biermann JS (2002). "Common benign lesions of bone in children and adolescents". J Pediatr Orthop. 22 (2): 268–73. PMID 11856945.
  12. Pichard DC, Boyce AM, Collins MT, Cowen EW (2014). "Oral pigmentation in McCune-Albright syndrome". JAMA Dermatol. 150 (7): 760–3. doi:10.1001/jamadermatol.2014.184. PMC 4933654. PMID 24671640.
  13. Nabhan ZM, West KW, Eugster EA (2007). "Oophorectomy in McCune-Albright syndrome: a case of mistaken identity". J Pediatr Surg. 42 (9): 1578–83. doi:10.1016/j.jpedsurg.2007.04.021. PMID 17848252.
  14. Ozawa T, Tateishi C, Shirakawa M, Murakami E, Ishii M, Harada T (2011). "Long-term follow-up of a case of cheek hyperpigmentation associated with McCune-Albright syndrome treated with Q-switched ruby laser". Dermatol Surg. 37 (2): 263–6. doi:10.1111/j.1524-4725.2010.01864.x. PMID 21272121.
  15. Chanson P, Salenave S, Orcel P (2007). "McCune-Albright syndrome in adulthood". Pediatr Endocrinol Rev. 4 Suppl 4: 453–62. PMID 17982395.

See also

External links

it:Sindrome di McCune-Albright-Sternberg

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