ESPE Abstracts

Background: McCune–Albright syndrome (MAS) is defined by skin, bone and glands disorders, due to activating mutations in the GNAS1. Clinical presentation is heterogeneous. Reports about GH excess in MAS patients are scarce.

Case report: We present the case of an 8-year-old male, previously diagnosed with mono-ostotic fibrous dysplasia of the skull, referred due to signs of pubertal development since the age of 6. The patient presented only 1 café-au-lait spot in the right subscapular area, puberty stage Tanner IV with asymmetric testicular development, growth above 97th percentile and accelerated bone age. Testosterone levels were elevated for age (0.65 ng/ml), but low for Tanner stage and testicular volume (8 and 10 ml). Basal gonadotrophins were measurable, with some stimulation after LHRH (maximal LH 2.1 mU/ml and FSH 0.8 mU/ml). IGF1 levels were +4 SDS and GH excess was proven after oral glucose load (minimal GH level 7.7 ng/dl). Hyperprolactinemia (224.8 ng/ml) was present, with normal serum cortisol and thyroid hormones. Genetic analysis of the GNAS in peripheral lymphocytes was normal, suggesting somatic mosaicism. Therapy with the GH-receptor blocker Pegvisomant has recently been started. ALS values dropped dramatically from +3.2 to +0.2 SDS after only one month of therapy, faster than IGF1 serum concentrations.

Discussion: There is little literature data regarding therapy with Pegvisomant in the paediatric population with GH excess. The main therapy target in this patient is lowering IGF1, as high levels represent a risk for compression of the optic nerve by the fibrotic bone tissue. Boys with MAS and signs of secondary sex characteristics are also rarely found in published reports, although testicular enlargement is more common. The inconsistent result of LHRH testing with a rather low testosterone level in this case speaks for an intermittent testicular activation, like is has been described in girls with MAS and pseudoprecocious puberty.