Endocrine Abstracts

Background: Vitamin D is important for calcium homeostasis. In granulomatous diseases including tuberculosis (TB), hypercalcaemia may be seen. Suspected mechanisms include elevated vitamin D sensitivity and increased extrarenal synthesis of 1,25-dihydroxyvitamin D [1,25(OH)₂D] by alveolar macrophages within granulomas. Prevalence of hypercalcaemia in TB patients vary worldwide, yet is rare in the UK. We present a case of hypercalcaemia in a patient with TB reactivation.

Case Report: Twenty-one-year-old female of African origin presented with dyspnoea, cough and weight loss. She moved to UK at the age of three. Fourteen years ago she was treated for latent TB. Chest x-ray and CT chest indicated TB reactivation while sputum culture confirmed Mycobacterium tuberculosis. She was commenced on quadruple anti-TB therapy. Additionally MRI Spine revealed impending cord compression at mid-thoracic vertebral level due to spinal TB. One month later, blood tests showed parathyroid hormone (PTH)-independent hypercalcaemia (Adjusted Calcium 2.77mmol/l, PTH <0.6pmol/l, 25OHD₃ 115 nmol/l). We requested multiple 1,25(OH)₂D levels, but faced issues processing the samples. Other causes of hypercalcaemia including malignancy were excluded after thorough biochemical and radiological investigations. It was concluded that hypercalcaemia was secondary to TB. Of note, patient developed acute kidney injury (AKI). Renal biopsy confirmed drug-induced interstitial nephritis likely due to Levofloxacin and was treated with prednisolone. Despite resolution of AKI, hypercalcaemia persisted. After one month of anti-TB and prednisolone treatment, calcium levels (2.53mmol/l) normalised.

Conclusion: Granulomatous-induced hypercalcaemia can pose a diagnostic challenge and a high index of suspicion enables early detection and treatment. As well as treating the underlying cause, glucocorticoid therapy is vital to reduce intestinal calcium absorption and inhibit synthesis of 1,25(OH)2D. We wish to highlight the importance of having a high clinical suspicion for granulomatous-induced hypercalcaemia, since prevalence is rare in the UK.