Unexpected Diffuse 18F-NaF Uptake in the Lung Parenchyma in a Patient With Severe Hypercalcemia Due to Myelomatosis

An 84-year-old man was admitted to the intensive care unit because of hypercalcemic crisis leading to acute renal failure needing dialysis. The patient had no other history of illness. However, because prostate-specific antigen levels were increased, the patient was referred to F-NaF PET/CT on suspicion of active skeletal metastases. The patient was finally diagnosed with myelomatosis. Although the skeletal uptake of F-NaF was without signs of focal metastasis, the F-NaF PET/CT scanning surprisingly revealed diffuse high accumulation of F-NaF in the lung parenchyma, possibly because of calcium deposition in the lung parenchyma associated to amyloidosis seen in patients with myelomatosis.