British Journal of Haematology | 2021
Circulating monocytes phagocytosing lymphocytes in anaerobic infection
Abstract
A 46-year-old man suffered an open fracture of his left index finger a month before presentation. The wound had been debrided and he had received empirical levofloxacin, but this was ineffective. A full blood count showed a normal platelet count and haemoglobin concentration, a mild leucocytosis of 10.59 9 10/l with 1.58 9 10/l monocytes. Ferritin was above 2000 lg/l. Other laboratory results indicated high level of serum procalcitonin (0.235 ng/ml) and triglycerides (4.6 mmol/l); fibrinogen was normal. Imaging showed no splenomegaly. A peripheral blood film showed monocytes with numerous, large cytoplasmic vacuoles (top and bottom left, all images 9100 objective). Phagocytosis of lymphocytes and occasional erythrocytes by monocytes was observed (all images). These clinical and laboratory features were suggestive of bacterial infection. Eikenella corrodens and Actinomyces odontolyticus were identified through anaerobic culture of material from deep in the infected tissue. The patient recovered and was discharged after a week of hyperbaric oxygen therapy. Prompt diagnosis and appropriate treatment of such cases may effectively prevent disease progression to pancytopenia and haemophagocytic syndrome. Haemophagocytosis can be a feature of a life-threatening hyperinflammatory state. It can be secondary to various underlying conditions, including infections, autoimmune diseases and haematological malignancies. The presence of phagocytosis of lymphocytes by circulating monocytes is extremely rare.