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Diffuse pulmonary ill-defined centrilobular opacities: Not only bronchiolitis

Published:March 25, 2022DOI:https://doi.org/10.1016/j.ejim.2022.03.023

      Abbreviations

      MPC
      metastatic pulmonary calcification
      rHPT
      renal hyperparathyroidism
      A 59 years old, non-smoker male presented with dry cough, and progressive asthenia. In his medical history he referred: parossistic atrial fibrillation first treated with three months amiodarone, then with radiofrequency ablation; mitral valve anuloplasty, pace maker placement, chronic anemia (Hb 7,6 g/dl), and a slight impairment of the renal function (creatinine blood level: 1,7 mg/dl; glomerular filtrate rate: 43 mL/min/1.73m2). CT of the thorax showed multiple ill-defined centrilobular nodules, associated with tiny and rare calcifications. Focal areas of tree-in-bud pattern were also present. The parenchymial changes had an upper and mid lung zones predomincance, and, in the slices through the upper abdomen, were associated with bilateral medullary nephrocalcinosis. The technetium-99 m (99mTc-MDP) scintigraphy showed an extensive uptake of the radiotracer in both lungs (right >left), the laboratory exams highlithed a slight increase of the parathyroid hormone (87 pg/ml) and of the 25 D vitamin (29 µg/L). Quantiferon was negative.
      What the diagnosis?
      Pulmonary metastatic calcification (PMC).
      The patients was diagnosed pulmonary metastatic calcification related to renal hyperparathyroidism (rHPT) in a 3B stage chronic renal failure, with mild to moderate increase of parathyroid hormone levels and failure of the kydney to convert 25 vitamin D to 1,25 vitamin D.
      MPC can be subdivided into benign and malignant, since several causes have been described in association: primary and secondary hyperparathyroidism, sarcoidosis, D hypervitaminosis, but also extensive bone malignancy, like parathyroid carcinoma, multiple myeloma, and lymphoma [
      • Chan E.D.
      • Morales D.V.
      • Welsh C.H.
      • McDermott M.T.
      • Schwarz M.I.
      Calcium deposition with or without bone formation in the lung.
      ,
      • Piciucchi S.
      • Barone D.
      • Gavelli G.
      • Dubini A.
      • Oboldi D.
      • Matteuci F.
      Primary hyperparathyroidism: imaging to pathology.
      ,
      • Romagnoli M.
      • Mourad G.
      • Serre I.
      • Senac J.P.
      • Paradis L.
      • Godard Ph.
      • Chanez P.
      Diffuse pulmonary calcinosis without calcium metabolism abnormalities in a renal transplant recipient.
      ]. By far, the most common cause of metastatic calcifications is seen in patients on hemodyalisis for chronic renal failure. Macroscopically, they consist of an amorphous substance or minute crystals, resulting from the release of calcium phosphate salts in the alveolar epithelium, in the bronchioles and in the media of pulmonary arterioles. They differ from the crystal-line hydroxyapatite more commonly found in vascular calcification [
      • Rosenthal D.I.
      • Chandler H.L.
      • Azizi F.
      • Schneider P.B.
      Uptake of bone imaging agents by diffuse pulmonary metastatic calcification.
      ]. Because MPC could be misinterpreted as pulmonary edema, or small-airways disease, the bone scintigraphy with bone-avid radiotracer 99mTc-MDP sort out any equivocal case [
      • Chan E.D.
      • Morales D.V.
      • Welsh C.H.
      • McDermott M.T.
      • Schwarz M.I.
      Calcium deposition with or without bone formation in the lung.
      ]. Their clinical relevance is the potential deterioration into a restrictive physiology, with a decreased diffusion capacity, and a resulting hypoxemia. Rarely, progressive respiratory failure may occur. The extent of the calcium deposition, does not correlate with the entity of calcium deposition, like in our case. So, beside treatment for chronic renal failure, the patient has been inserted in an annually follow-up program with pulmonary function tests and CT scan of the thorax [
      • Belém L.C.
      • Zanetti G.
      • Souza Jr, A.S.
      • Hochhegger B.
      • Guimarães M.D.
      • Nobre L.F.
      • Rodrigues R.S.
      • Marchiori E.
      Metastatic pulmonary calcification: state-of-the-art review focused on imaging findings.
      ] Fig. 1.
      Fig. 1:
      Fig. 1Multiple ill-defined centrilobular nodules, some of them calcified are present in both lungs, with relative prevalence for mid to upper lung zones and for the right upper lobe (b, red circle), where the scintigraphy demonstrates a diffuse uptake of the radiotracer (e,f - green circles). Upper abdomen images show bilateral medullary calcification, suggestive of nephrocalcinosis (g, yellow arrow).

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