Elevated serum adenosine deaminase levels in secondary hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory condition caused by activated T cells and macrophages. Adenosine deaminase (ADA) plays an important role in immune regulation, especially in the proliferation, maturation, and differentiation of lymphocytes. Its role has been studied in inflammation and malignancy. Here, we present for the first time the alteration of ADA in secondary HLH (sHLH).

Serum ADA levels were measured in 20 cases with lymphoma-associated hemophagocytic syndrome (LAHS), 15 with infection-associated hemophagocytic syndrome (IAHS), six with macrophage activation syndrome (MAS) as experimental group. Additionally, we enrolled 20 cases with lymphoma, 15 with infection, six with autoimmunity who were all not associated with HLH as conditional control group and 20 healthy subjects as blank group. We also demonstrated the ADA levels in 20 LAHS cases and 21 benign disease-associated HLH cases (IAHS and MAS).

Serum ADA levels were significantly higher in patients with LAHS, IAHS, and MAS compared to the healthy subjects (P < 0.001) and conditional control group (P < 0.05). Serum ADA levels of patients with LAHS were significantly higher than benign disease-associated HLH cases (P < 0.05). The optimum ADA cutoff point for LAHS was 89.25 U/L, with a sensitivity and specificity of 85.0% and 76.2%, respectively.

Serum ADA levels were increased in sHLH suggesting a partial role of activated T-cell response in the disease pathophysiology. Serum ADA levels were particularly higher in LAHS and probably be a potential indicator of underlying lymphoma in sHLH patients.