Metastatic pulmonary calcification: State-of-the-art review focused on imaging findings

Abstract

Metastatic pulmonary calcification (MPC) is a subdiagnosed metabolic lung disease that is commonly associated with end-stage renal disease. This interstitial process is characterized by the deposition of calcium salts predominantly in the alveolar epithelial basement membranes. MPC is seen at autopsy in 60-75% of patients with renal failure. It is often asymptomatic, but can potentially progress to respiratory failure. Chest radiographs are frequently normal or demonstrate confluent or patchy airspace opacities. Three patterns visible on high-resolution computed tomography have been described: multiple diffuse calcified nodules, diffuse or patchy areas of ground-glass opacity or consolidation, and confluent high-attenuation parenchymal consolidation. The relative stability of these pulmonary infiltrates, in contrast to infectious processes, and their resistance to treatment, in the clinical context of hypercalcemia, are of diagnostic value. Scintigraphy with bone-seeking radionuclides may demonstrate increased radioactive isotope uptake. The resolution of pulmonary calcification in chronic renal failure may occur after parathyroidectomy, renal transplantation, or dialysis. Thus, the early diagnosis of MPC is beneficial. The aim of this review is to describe the main clinical, pathological, and imaging aspects of MPC.

Nano-hydroxyapatite modulates osteoblast lineage commitment by stimulation of DNA methylation and regulation of gene expression

“…Accordingly, these two ions have a particularly important relationship in biology and can exist in multiple forms (ratios) such as mono, di, and tri-calcium phosphate (ratios from 0.5 to 1.5) [2]. Recent studies have suggested that various forms of nano-Calcium-Phosphate (CaP) synthesized by the body are associated with functional mineralization of bone and pathological calcification of vascular smooth muscle [3–7]. Nano-sized hydroxyapatite (nano-HAp) is generated endogenously by osteoblasts in the form of matrix vesicles as the initiator of bone formation in the skeleton, [8] as well as in pathological calcification of cartilage and vasculature [9–12] and can be deposited in soft tissues in the form of dystrophic and metastatic calcifications, [13, 14] although the origins are not completely understood.…”

Metastatic pulmonary calcification in end-stage renal failure

“…2 Among those who have symptoms, the manifestations can include progressive dyspnea, hypoxemia, hemoptysis and, rarely, alveolar hemorrhage and fulminant respiratory insufficiency. 3 The differential diagnosis includes end-stage renal disease, malignancies (such as multiple myeloma) and dystrophic pulmonary calcification (Appendix 2, available at www.cmaj.ca/lookup/ suppl/doi:10.1503/cmaj.150778/-/DC1). 3,4 High-resolution CT typically shows poorly defined centrilobular nodules with ground glass opacities 3-10 mm in diameter.…”

“…3 The differential diagnosis includes end-stage renal disease, malignancies (such as multiple myeloma) and dystrophic pulmonary calcification (Appendix 2, available at www.cmaj.ca/lookup/ suppl/doi:10.1503/cmaj.150778/-/DC1). 3,4 High-resolution CT typically shows poorly defined centrilobular nodules with ground glass opacities 3-10 mm in diameter. 2 CT detects existing calcium deposits that may be inactive, whereas bone scintigraphy identifies areas of active calcium deposition.…”

“…2 Pulmonary function tests often yield normal results, but may show reduced diffusion capacity and a restrictive pattern. 3 The optimal treatment for metastatic pulmonary calcification remains unknown. Patients with asymptomatic nonprogressive disease may not need any intervention.…”

“…The mainstay of therapy is normalization of calcium and phosphate biochemistry. 3 It is unclear whether vitamin D supplementation should be discontinued. 3 An increase in the frequency of hemodialysis is generally indicated.…”