[Pulmonary infiltrates associated with chronic elevation of blood circulating monocytes]

Chronic myelomonocytic leukemia (CMML) is a clonal myeloid neoplasm with myelodysplastic and myeloproliferative features. Although inflammatory and extramedullary manifestations occur, pulmonary involvement is rare. We describe steroid-responsive pulmonary and systemic inflammatory involvement revealing CMML.

A 74-year-old man with a 3-year history of unclassified inflammatory polyarthritis presented with fever, hypoxemic respiratory failure, inflammatory wrist and ankle arthralgia, and pruritic maculopapular lesions. He required 5L/min oxygen. Laboratory studies showed CRP 216mg/L, hemoglobin 9.5g/dL, leukocytes 17.2G/L, and monocytosis 8G/L. Chest computed-tomography (CT) revealed a right lower-lobe mixed opacity, smooth interlobular septal thickening, and micronodules. Bronchoalveolar lavage was lymphocyte-predominant and sterile; antinuclear antibodies and anti-neutrophil cytoplasm antibodies were negative. Empirical piperacillin-tazobactam and diuretics did not improve inflammation or oxygen requirement. Skin biopsy showed an angiocentric infiltrate consistent with clonal monocytic infiltration. Bone marrow examination demonstrated dysmyelopoiesis, monocytic hyperplasia, and 11.5% blasts, confirming CMML. Sequencing with next generation sequencing identified DNMT3A, IDH2, SRSF2, RUNX1, and ASXL1 mutations. Prednisone 0.3mg/kg/day led to oxygen weaning, disappearance of fever, arthritis and rash, reduction in inflammatory markers and monocytosis and complete CT resolution of the interstitial lung disease within 7 days.

CMML-associated inflammatory pulmonary disease should be considered in unexplained infiltrates in patients suspected with CMML or persistent monocytosis after exclusion of infection, overload, and autoimmune disease.