Adult T-cell leukemia with hypercalcemia-induced metastatic calcification in the lungs due to production of parathyroid hormone-related protein

Reprint of: Unusual non-neoplastic lesions of the lung

Many nonneoplastic conditions that may affect the lung are in reality rare or unusual manifestations of metabolic processes, inflammatory conditions, or unknown etiology. Because of their rarity, they can often be confused with malignant neoplasms. Familiarity with these conditions not only will expedite further treatment for these patients but also will avoid the process of more tests or unnecessary surgical procedures. The nomenclature for some of those conditions is still controversial. The clinical outcome of these conditions can be quite variable, with some patients surviving a long number of years and others eventually succumbing to the disease. We will limit our discussion in this review to four of these conditions, including inflammatory pseudotumor (inflammatory myofibroblastic tumor), placental transmogrification of lung, alveolar microlithiasis, and metastatic calcification. Although these lesions are not part of the gamut of neoplastic conditions affecting the lung, they are nonetheless important to recognize, as their outcome may not necessarily be an innocuous one.

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

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.

[Pulmonary metastatic calcification]

INTRODUCTION

The lung is the organ most frequently involved by metastatic calcification. This condition is probably under-diagnosed, the patients usually being asymptomatic. This article summarizes the current knowledge concerning pulmonary metastatic calcification.

BACKGROUND

The pathogenesis of pulmonary metastatic calcification is not well known, but it involves phosphate-calcium balance, renal function and pH. The most frequently encountered aetiologies are hyperparathyroidism, neoplastic bony lesions, and renal failure. The definitive diagnosis is achieved by histology, radiological examinations being insensitive. The clinical manifestations are various and can include a pulmonary restrictive syndrome, diffusion abnormalities, hypoxaemia and respiratory failure. The latter can be severe and influence the prognosis adversely: 19 cases of fatal pulmonary metastatic calcification have been reported. The treatment is aetiological and symptomatic.

VIEWPOINT

The prognostic factors for a poor outcome of this potentially lethal condition remain to be determined. The management of asymptomatic patients is also uncertain.

CONCLUSIONS

Pulmonary metastatic calcification is a rare condition of complex pathogenesis. The clinical manifestations are varied, ranging from asymptomatic to severe, even fatal.

Pathogenesis of Metastatic Calcification and Acute Pancreatitis in Adult T-Cell Leukemia under Hypercalcemic State

Human T-cell leukemia virus type-1 (HTLV-1) is the causative agent of adult T-cell leukemia (ATL). Hypercalcemia is common in patients with ATL. These patients rarely develop metastatic calcification and acute pancreatitis. The underlying pathogenesis of this condition is osteoclast hyperactivity with associated overproduction of parathyroid hormone-related protein, which results in hypercalcemia in association with bone demineralization. The discovery of the osteoclast differentiation factor receptor activator of nuclear factor-κB ligand (RANKL), its receptor RANK, and its decoy receptor osteoprotegerin (OPG), enhanced our understanding of the mechanisms of ATL-associated hypercalcemia. Macrophage inflammatory protein-1-α, tumor necrosis factor-α, interleukin-1, and interleukin-6 are important molecules that enhance the migration and differentiation of osteoclasts and the associated enhanced production of RANKL for osteoblast formation. In this paper, we focus on metastatic calcification and acute pancreatitis in ATL, highlighting recent advances in the understanding of the molecular role of the RANKL/RANK/OPG system including its interaction with various cytokines and calciotropic hormones in the regulation of osteoclastogenesis for bone resorption in hypercalcemic ATL patients.

Unusual non-neoplastic lesions of the lung

Many nonneoplastic conditions that may affect the lung are in reality rare or unusual manifestations of metabolic processes, inflammatory conditions, or unknown etiology. Because of their rarity, they can often be confused with malignant neoplasms. Familiarity with these conditions not only will expedite further treatment for these patients but also will avoid the process of more tests or unnecessary surgical procedures. The nomenclature for some of those conditions is still controversial. The clinical outcome of these conditions can be quite variable, with some patients surviving a long number of years and others eventually succumbing to the disease. We will limit our discussion in this review to four of these conditions, including inflammatory pseudotumor (inflammatory myofibroblastic tumor), placental transmogrification of lung, alveolar microlithiasis, and metastatic calcification. Although these lesions are not part of the gamut of neoplastic conditions affecting the lung, they are nonetheless important to recognize, as their outcome may not necessarily be an innocuous one.

Imaging of diffuse metastatic and dystrophic pulmonary calcification in children after haematopoietic stem cell transplantation

The authors describe three cases of diffuse pulmonary calcification; two metastatic in children with acute transitory renal failure and the other dystrophic in a child with leukaemia. All three patients underwent haematopoietic stem cell transplantation (HSCT). Chest radiographs disclosed diffuse calcification within the lungs. The distribution of this calcification was bilateral but asymmetric. Diagnosis was made in two cases by high resolution computed tomography (HRCT) and in one case by HRCT and bone scan. Radiological characteristics, scintigraphic features, pathological mechanism and clinical outcome of such pulmonary calcification are discussed.