Giant lymph node hyperplasia (GLH) is an unusual form of benign lymphoid hyperplasia which, although it often occurs in the mediastinum, has not previously been reported to involve the thymus. In this report, a case of GLH with involvement of the thymus and with associated nephrotic syndrome and myelofibrosis is presented. The significance of the association of these conditions with GLH is discussed, including the possibility that some or all of the patient's abnormalities may have been related via an abnormal immune mechanism.