Endocrine Abstracts

Introduction: Fibrous dysplasia is a rare non hereditary genetic disorder in which normal bone marrow is replaced with expansile fibro-osseous lesions, resulting in pain, reduction in bone strength and fractures. It can manifest as monostatic (single bone) or polyostotic (multiple bones) disease with the craniofacial skeleton, long bones and ribs commonly being affected. Extra skeletal features such as skin hyperpigmentation and hyper functioning endocrinopathies may be present if associated with McCune-Alright syndrome, originating from a mutation in the GNAS gene.

Clinical Case: A 62 year old gentleman was referred to Hepatology in 2017 with an isolated rise in alkaline phosphatase (ALP) of 233 U/l (30-130 U/l) for the preceding 4 years. He was asymptomatic but noted to have bilateral hearing aids. He was extensively investigated with a full liver screen, ultrasound and MRCP which were all normal. He was subsequently seen by Rheumatology 7 years later with a persisting rise in ALP, now 356 U/l (30-130 U/l) but with no symptoms suggestive of Paget’s disease. Calcium, vitamin D, phosphate, magnesium and renal function were within the normal range. A nuclear medicine bone scan showed extensive heterogenous marked uptake in the skull and mild uptake in L1. As his presentation was not typical for Paget’s disease a CT head and skull base was performed which showed very extensive bony ‘ground glass’ change throughout the majority of this skull base and occipital, most characteristic for extensive, but slightly atypical, fibrous dysplasia with radiological involvement of the optic canals bilaterally. On examination he had no relevant cutaneous changes, no changes in face shape, normal thyroid and testicular ultrasound and no evidence of hyperfunctioning endocrinopathy. Current management strategies focus primarily on symptom control and although bone therapy has not yet been initiated he is keeping a symptom diary.

Conclusion: Fibrous dysplasia should be on the list of differentials for cases that appear as an asymptomatic rise in ALP. Presence of ground glass changes and location of lesions (fibrous dysplasia has a predilection for long bones) may be features that favour fibrous dysplasia. This case demonstrates the importance of implementing a multisciplinary approach to management and the often prolonged diagnostic journey these patients encounter.