Spleen enlargement is a common finding in acute Puumala hantavirus infection and it does not associate with thrombocytopenia.

The pathogenesis of thrombocytopenia in Puumala hantavirus (PUUV) infection is probably multifactorial. We aimed to evaluate the possible spleen enlargement during acute PUUV infection, and to determine its association with thrombocytopenia and disease severity. Magnetic resonance imaging (MRI) of the spleen was performed in 20 patients with acute PUUV infection. MRI was repeated 5-8 months later. The change in spleen length was compared with markers describing the severity of the disease. In all patients, the spleen length was increased in the acute phase compared with the control phase (median 129 mm vs 111 mm, p < 0.001). The change correlated with maximum C-reactive protein value (r = 0.513, p = 0.021) and inversely with maximum leukocyte count (r = -0.471, p = 0.036), but not with maximum serum creatinine level or minimum platelet count. Enlarged spleen, evaluated by MRI, was shown to be a common finding during acute PUUV infection. However, it does not associate with thrombocytopenia and acute kidney injury.