Infiltrative, inflammatory or thromboembolic processes in the parenchyma of the spleen can cause a functional loss of the organ. This phenomenon is called functional asplenia and occurs as a complication especially in sickle cell disease, lupus erythematosus and after bone marrow transplantation. We present the case of a patient with Crohn's disease under immunosuppressive therapy who developed a spontaneous covered spleen rupture in the course of a septic shock with DIG due to a Varizella zoster infection. Later on, sonography showed a diminution of the spleen size. No flow signals could be derived by colour doppler measurements from the spleen. Because of the colour doppler findings we suspected a functional asplenia which was then verified by spleen scintigraphy and Howell-Jolly-Bodies in the blood count. Remarkably, the Crohn's disease remains in complete remission since the development of the functional asplenia (for 4 years now). The underlying pathomechanism remains unclear.