Endocrine Abstracts

Introduction: McCune-Albright Syndrome (MAS) is a rare genetic disorder that often affects bones and causes polyostotic fibrous dysplasia (FD). Craniofacial FD is rare and may present as facial asymmetry, orbital pain, or vision loss due to compressive optic neuropathy (ON), which can significantly impact quality of life (QOL). We present a case of orbital FD.

Case: A 15-year-old boy presented with a one-year history of fluctuating swelling above his left eye and temple, limiting eye opening. MRI revealed a 4 x 3.3 x 3.3 cm mass at the left orbit, displacing the globe and indenting the basal frontal lobe, suggestive of FD. Further skeletal survey showed no additional bone involvement. Genetic studies confirmed McCune-Albright syndrome, with normal endocrine investigations including LH/FSH, IGF-1, testosterone, thyroid function, and bone profile. He attained puberty at the same age as his peers. He later developed severe pain over his left orbit, due to soft tissue compression and expansion of fibrous bone. Zoledronate infusions were started due to persistent, painful swelling unresponsive to simple analgesia, initially at a paediatric dose of 0.025-0.05 mg/kg. This resulted in marked improvement in symptoms and QOL. ALP also reduced from 134U/l to 86U/l.

Discussion: MAS is caused by sporadic mutations in the GNAS gene and is characterised by fibrous dysplasia, café-au-lait spots, and endocrine disruptions. Orbital FD, particularly fluctuating in size, is less well-recognised and led to a delay in diagnosis in this case. Management of MAS is primarily symptom-targeted and a multidisciplinary approach is imperative due to the diverse spectrum of presentations. Although bisphosphonate therapy can effectively help in managing bone pain, it has a limited impact on bone disease progression. Therefore, long-term, continuous bisphosphonate therapy is not recommended. Instead, intermittent use with regular assessment is preferred, particularly in the paediatric population where bone mass has not peaked.