We present a female patient from Somalia with an acute lymphoblastic leukemia, who received an allogeneic bone marrow transplantation (BMT) and developed several periods of moderate to severe pulmonary symptoms that were accompanied by pulmonary infiltrates and peripheral blood eosinophilia. After several recurrences an open lung biopsy was performed, which initially gave rise to the diagnosis parasitic infection. Later on this diagnosis was questioned and it was suggested that the structures were artifacts that might have been aspirated. Nevertheless, after the immediately given antihelminthic treatment no peripheral blood eosinophilia occurred anymore, but at that point of time pulmonary function was already severely hampered and eventually led to a lethal complication. With the worldwide increasing migration from Third World countries with a high prevalence of parasitic infections, more patients will receive immunosuppressive therapies in countries less familiar with parasites. This may complicate diagnostic procedures, prevent early recognition and delay adequate treatment. Specific screening for opportunistic parasitic infections of the population at risk before BMT and a great awareness for these infections is strongly recommended.