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Open access

Mike Lin and Kirtan Ganda

Summary

We present the case of a 60-year-old female who developed repeated atraumatic stress fractures. She was initially diagnosed with osteoporosis based on her dual-energy X-ray absorptiometry (DXA) scan bone mineral density (BMD) T-scores and started on denosumab therapy. Secondary osteoporosis screen revealed abnormal myeloma screen and low serum phosphate levels. It was thought that the patient had multiple myeloma with associated Fanconi-related tubular dysfunction. However, fibroblast growth factor-23 (FGF-23) levels were grossly elevated, making Fanconi syndrome unlikely. The patient was subsequently diagnosed with two separate conditions, namely cardiac amyloid light-chain (AL) amyloidosis and FGF-23-related hypophosphataemia, likely due to tumour-induced osteomalacia. This case highlights the importance of excluding osteomalacia as a cause of low BMD and checking FGF-23 levels in the workup for hypophosphataemia.

Learning Points

  • Tumour-induced osteomalacia is a difficult diagnosis as the tumour is often small and slow growing. Imaging may fail to identify a tumour, and treatment therefore consists of calcitriol and phosphate replacement.

  • Tumour-induced osteomalacia should be suspected in the adult presenting with new-onset hypophosphataemia, elevated FGF-23 levels and isolated renal phosphate wasting.

  • Serum phosphate is not part of the routine chemistry panels. Routinely checking phosphate levels prior to initiating antiresorptive therapy is warranted.

  • DXA cannot distinguish low bone mineral density due to osteoporosis from osteomalacia. Antiresorptive therapy should be avoided in osteomalacia due to the risk of clinical and radiographic deterioration.

Open access

Mike Lin, Venessa Tsang, Janice Brewer, Roderick Clifton-Bligh, and Matti L Gild

Summary

Lymphocytic hypophysitis is a rare neuroendocrine disease characterised by an autoimmune inflammatory disorder of the pituitary gland. We report a 50-year-old woman who presented with headaches and bilateral sixth cranial nerve palsies. MRI of the pituitary revealed extensive fibrosis involving the sellar and extending into both cavernous sinuses causing bilateral occlusion of the internal carotid arteries (ICA). Transphenoidal biopsy confirmed the diagnosis of infiltrative fibrotic lymphocytic hypophysitis. Symptoms resolved with high dose of oral steroids but relapsed on tapering, requiring several treatments of i.v. pulse steroids over 8 months. Rituximab combined with mycophenolate mofetil was required to achieve long-term symptom relief. Serial MRI pituitary imaging showed stabilisation of her disease without reduction in sellar mass or regression of ICA occlusion. The patient’s brain remained perfused solely by her posterior circulation. This case demonstrates an unusual presentation of a rare disease and highlights a successful steroid-sparing regimen in a refractory setting.

Learning points:

  • Lymphocytic hypophysitis is a rare inflammatory disorder of the pituitary gland. In exceptional cases, there is infiltration of the cavernous sinus with subsequent occlusion of the internal carotid arteries.

  • First-line treatment of lymphocytic hypophysitis is high-dose glucocorticoids. Relapse after tapering or discontinuation is common and its use is limited by long-term adverse effects.

  • There is a paucity of data for treatment of refractory lymphocytic hypophysitis. Goals of treatment should include improvement in symptoms, correction of hormonal insufficiencies, reduction in lesion size and prevention of recurrence.

  • Steroid-sparing immunosuppressive drugs such as rituximab and mycophenolate mofetil have been successful in case reports. This therapeutic combination represents a viable alternative treatment for refractory disease.