Endocrine Abstracts

Background: Children with undiagnosed coeliac disease are at risk of low bone mineral density (BMD), but whether this translates to fracture predisposition is unclear. In adults with coeliac disease anti-osteoprotegerin (anti-OPG) antibodies have been identified. OPG inhibits RANK ligand activation of osteoclastic bone resorption, and thus anti-OPG antibodies promote bone loss. We report a case of osteoporosis with elevated anti-OPG antibodies in a child with coeliac disease.

Case: An 11-year old boy presented with a 6-month history of back pain. There was a prior history of low-trauma fractures but no family history of osteoporosis or fracture. Sclerae were white and dentinogenesis imperfecta was not present. Radiographs demonstrated extensive thoracic and lumbar vertebral compression fractures. Investigations for secondary osteoporosis revealed elevated tissue transglutaminase antibodies (anti-tTG) despite no reported symptoms of coeliac disease. Dual-energy X-ray absorptiometry (DXA) demonstrated whole body and lumbar spine BMD Z-scores of -2.0 and -4.2, respectively. Duodenal biopsy confirmed coeliac disease, and a gluten-free diet (GFD) was commenced. Bone biopsy showed a borderline mineralisation defect with mild osteopenia compatible with malabsorption. An osteogenesis imperfecta gene panel (comprising COL1A1, COL1A2, IFITM5 and those listed in the 100,000 genomes project) was normal. Anti-OPG antibodies were performed due to the reported association with coeliac disease; these were elevated at 65ng/mL (normal range <33ng/mL). Treatment with intravenous zoledronate (0.05 mg/kg every six months) was commenced. Anti-tTG normalised with gluten-free diet. Serial DXA scans have demonstrated progressive increase in BMD (BMD Z-scores at 15.6 years old: whole body 0.4, lumbar spine -0.6). There have been improvements in vertebral morphometry, no new vertebral fractures, and marked improvement in bone pain. He is approaching final adult height on the 50th-75th centile (target range 9th-91st centile). He has not sustained any further low-trauma fractures.

Conclusion: Undiagnosed coeliac disease is an uncommon cause of childhood osteoporosis, but this diagnosis should not be missed. To our knowledge, multiple vertebral fractures have not previously been reported as the presenting feature of childhood-onset coeliac disease. Confirmation of anti-OPG antibodies supports coeliac disease as the cause of osteoporosis in this patient. Bisphosphonates, in combination with GFD, were effective at improving bone outcomes.