Endocrine Abstracts

Introduction: McCune-Albright syndrome is a rare, heterogenous disorder, consisting of at least two of the following three features: polyostotic fibrous dysplasia, café-au-lait skin pigmentation and autonomous endocrine hyperfunction. We present the case of a patient with an atypical presentation of McCune Albright syndrome (MAS) and severe fibrous dysplasia lesions.

Case report: An 18-year-old girl diagnosed with MAS (at the age of four) was referred to our clinic for a first endocrine evaluation. She had a history of allergodermia and recurrent wheezing from an early age (8 months and 1.8 years respectively), with the subsequent development of a limp (2.5 years old). She had attained menarche at 3.3 years of age (currently having normal spontaneous menses) and had multiple pathologic fractures during childhood, the first being a proximal femoral shaft fracture (4 years old), for which she underwent 2 surgeries, resulting in shortening of the left leg. Prior X-ray imaging and CT scans showed left coxa vara, tibial bowing, cortical thinning, and multiple sclerotic and lytic lesions suggesting polyostotic fibrous dysplasia (confirmed by left femur biopsy). On physical examination, she had hyperpigmented macules with irregular margins, leg length discrepancy, macrocephaly with clover shaped skull and facial asymmetry. Her height was 165 cm, within her target height range (172.5+/−10 cm). Laboratory data revealed normal calcium, phosphorus and parathyroid hormone levels, vitamin D deficiency, very high alkaline phosphatase levels (15.6×upper limit of normal, ULN) and elevated bone turnover markers. Insulin-like growth factor 1 was within the normal range, but she had unsuppressed growth hormone (GH) levels following 75 g oral glucose load (nadir GH 1.72 ng/ml) and elevated random GH (10.56 ng/ml). Prolactin levels were slightly elevated (1.29×ULN). Pituitary imaging found a sellar mass of 5/7/6.7 mm. Thyroid ultrasonography showed several micronodules, with normal thyroid function. No other endocrinopathies were found. Antiresorptive agents such as bisphosphonates (pamidronate) or anti-RANKL antibody (denosumab) are taken into consideration as therapeutic options.

Conclusion: Diagnosis of MAS is usually established on clinical grounds, but the presenting signs and symptoms are highly variable. Although GH and prolactin excess are common (21%)¹, the clinical expression can be ‘whispering’, as in our case. As all MAS features have a varied time of presentation, early referral to an endocrinologist and meticulous follow-up and management is essential.

References: Christoforidis A et al, McCune-Albright syndrome: growth hormone and prolactin hypersecretion.J Pediatr Endocrinol Metab. 2006; 19 Suppl 2:623–625