The aim of the paper is to present a case of a 5-year-old boy hospitalised because of recurrent high temperature and reddish blue infiltration of skin and hypodermis lasting 3 months. Because of pancytopenia and hepatomegaly, we suspected a proliferative disease of the haematopoietic or lymphatic system. Several bone marrow biopsies, did not show neoplastic changes. Serological tests excluded virus and animal borne infections. In the histopathologic examination of skin and hypodermis biopsy there was an inflammatory infiltration of the adipose tissue without features of vessel inflammation (the Weber-Christian syndrome). Al though steroid therapy was applied, the infiltration of the adipose tissue did not regress, while liver dysfunction symptoms intensified and pancytopenia and fever continued. The patient died with symptoms or respiratory and circulatory failure. This case of a 5-year-old boy is presented because of extreme diagnostic difficulties, which occurred at each phase of investigations. The repeated tests, as well as several verifications of the sampled histopathological material did not bring any unequivocal proof of the postulated diagnosis.