Pulmonary infiltration as the initial manifestation of chronic lymphoproliferative disorder of natural killer cells: a case report and literature review.

BACKGROUND Chronic lymphoproliferative disorder of natural killer cells (CLPD-NK) is an extremely rare haematological disease. To the best of our knowledge, pulmonary infiltration in CLPD-NK has not been reported before. Our case study aimed to present the clinical characteristics, chest computed tomography (CT) findings, and flow cytometry immunophenotyping (FCI) results of an unusual case of migratory pulmonary infiltration in a patient with CLPD-NK. CASE PRESENTATION A 51-year-old female patient was admitted to our hospital on October 8, 2019. Eight months before this visit, she had been diagnosed with pneumonia in a community hospital with 1 month of low-grade fever and had recovered after oral antibiotic administration. During follow-up, the patient presented with persistent peripheral blood (PB) lymphocytosis and ground-glass opacities on lung CT scans without any symptoms and signs or any evidence of infectious, allergic or autoimmunity pulmonary diseases. Abnormal NK cells were identified in the PB, bone marrow and bronchoalveolar lavage fluid (BALF) using FCI in our hospital. Eventually, the patient was diagnosed with pulmonary infiltration of CLPD-NK. The patient had an indolent clinical course without symptoms, hepatosplenomegaly or palpable lymphadenopathy and did not receive any therapy. The patient has remained in a good performance status 13 months after the diagnosis. CONCLUSIONS Our study described a unique case of pulmonary infiltration in a patient with CLPD-NK. The present case highlights the importance of FCI of the BALF in patients with lymphocytosis and pulmonary shadows to avoid misdiagnosis.