What is the prognosis of McCune-Albright syndrome (MAS)?

Updated: Jan 05, 2021
  • Author: Gabriel I Uwaifo, MD; Chief Editor: George T Griffing, MD  more...
  • Print

Apart from the small subgroup of patients with increased perioperative mortality and those patients who develop malignancies, McCune-Albright syndrome (MAS) is not associated with a significantly increased mortality. In general, patients achieve a normal life span. Mortality and morbidity related to MAS result from the fractures, malignancies, endocrine disorders, and other conditions associated with this syndrome. The symptom and disability burden of MAS can be quite high, owing to the associated chronic pain and deformities, as well as the sequelae of chronic multihormonal endocrinopathies. Thus, the prognosis varies according to the manifestations of MAS.

With precocious puberty, the prognosis depends on the duration of premature estrogen exposure. Early puberty is not a life-threatening condition and does not seem to lead to problems after true, centrally mediated puberty begins at an appropriate age. Early breast development and vaginal bleeding can be accompanied by loss of adult height potential. Reduction of height potential depends on the degree of bone age advancement that occurs during the periods of early estrogen exposure.

A study of 16 girls and 10 boys with MAS found (1) that MAS occurs slightly more frequently in girls than in boys, (2) that peripheral precocious puberty (PPP) in MAS occurs significantly more frequently and at a younger age in girls than in boys, (3) that PPP in boys with MAS correlates with bilateral testicular enlargement, (4) that unilateral macroorchidism can occur, and (5) that testicular microlithiasis might function as another marker for MAS in males. [27]

Moreover, a literature review by Aversa et al indicated that at presentation, macroorchidism is the most common testicular abnormality related to MAS. In addition, the study found that in MAS, an association does not always exist between macroorchidism and clinical and biochemical evidence of peripheral precocious puberty. [28]

FD may have severe effects, including pathologic fractures, facial disfigurement, and vision and hearing problems. It is difficult to treat effectively. Current therapies focus on treating complications of FD, rather than on preventing it from developing. Current studies using bisphosphonates are promising, though it is unclear whether bisphosphonates significantly reduce the morbidity associated with these lesions.

Hyperthyroidism can cause severe failure to thrive in infants and young children, decreased attention span, and osteoporosis. Tachycardia resulting from severe hyperthyroidism may complicate or trigger a cardiac event. Radioiodine (131 I) ablation or thyroidectomy treats hyperthyroidism effectively. The long-term prognosis is excellent with adequate thyroid hormone replacement.

Infantile Cushing syndrome can cause severe growth failure, poor muscle tone, and hypertension. Permanent effect on growth potential is also possible. Comorbid heart and liver disease are poor prognostic markers and may indicate the need for prompt adrenalectomy. [29]

The long-term prognosis for infantile Cushing syndrome depends on adequate replacement of both mineralocorticoids and glucocorticoids. Individuals remain at risk for significant morbidity or mortality due to adrenal insufficiency during times of severe stress and should receive stress doses of hydrocortisone on an emergency basis.

Hypophosphatemia causes rickets and short stature; the pathophysiology of hypophosphatemic rickets, as well as the need for long-term therapy with calcitriol and phosphorus supplementation in these cases, increases the risk of nephrocalcinosis and loss of renal function over time.

Gigantism or acromegaly can occur, carrying a risk of glucose intolerance, hypertriglyceridemia, hypertension, and mild myopathy. GH secretion in MAS is difficult to treat effectively. Octreotide acetate or pegvisomant has proved effective in many cases, but not all. Furthermore, radiation treatment of the adenoma increases the risk of malignant change in areas of FD in the radiation field. The long-term prognosis in refractory cases of acromegaly is poor.

Although 2 long-term follow-up studies have shown no increased risk of premature death, several authors have noted unexplained sudden death in patients with a severe phenotype. Patients may have multiple endocrine, cardiac, GI, central nervous system (CNS), hematopoietic, and hepatic manifestations, all of which can contribute to significant morbidity. Although no arrhythmias have been detected in individuals with MAS, this is the presumed mechanism of sudden death.

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!