A 68-year-old woman presented to the emergency department with a 4-month history of progressive lower limb weakness and lethargy associated with multiple small and large joint pains, worst in the shoulders, hips, elbows, and hands. She had lost 12 kilograms (17% body weight) over 12 months and was no longer able to mobilise or perform her activities of daily living without assistance. Over the past 2 months, her pain and proximal myopathy had resulted in several falls.
Her medical history included a left lung transplant in 2018 for pulmonary fibrosis and emphysema. Transplantation was complicated by Lomentospora prolificans colonisation with mycetoma formation in the right lung requiring long-term antifungal therapy. She was diagnosed with osteoporosis in 2017 and had been receiving denosumab since. She had no history of fragility fracture. She had type two diabetes and primary hypothyroidism, which were well controlled.
Initial investigations revealed hypophosphataemia (0.58 mmol/L) and secondary hyperparathyroidism (PTH 25.6 pmol/L, corrected calcium 2.30 mmol/L) with normal 25-hydroxyvitamin D and renal function. Her bone turnover markers were unsuppressed. A 24-hour urine collection demonstrated renal calcium conservation and phosphate wasting. Serum FGF-23 was elevated (189 ng/L).
Skeletal x-rays showed widespread ill-defined calcific deposits consistent with thick periosteal reactions in the hands, forearms, shoulders, and hips. A radionuclide bone scan demonstrated multiple areas of abnormal tracer uptake corresponding to radiological areas of periosteal new bone formation. FDG-PET, DOTATATE-PET, and sestamibi parathyroid scintigraphy were normal.
DXA showed normal T-scores in the lumbar spine and osteopenic T-scores in the right femoral neck (-2.0 SD). Right total hip bone density had increased 25% over 3 years.
The emergence of widespread nodular periostitis and secondary hyperparathyroidism after transplantation pointed to an acquired cause. Further investigation was required before a basic treatment could be tried.