Abstract • 89

Nijmegen Breakage Syndrome is a rare immunodeficiency, belonging to the DNA repair syndromes. The characteristics are microcephaly, short stature, immunodeficiency, chromosomal instability with rearrangements of chromosomes 7 and/or 14, X-ray hypersensitivity and predisposition to cancer. Now some 60 patients have been recognized. Of them 22 patients, varying in age from 1 to 22 years, developed a malignancy. A lymphoma was found in 16 patients. The majority of these are B-cell lymphoma's. The other six had leucaemia (3), glioma (1), medulloblastoma (1) and rhabdomyosarcoma (1).

Malignancy has been found in both patients with a mutation of the "common founder" type (a truncating 5 bp deletion, 667-661delACAAA) and patients with other mutation in the NBS1 gene.

A proposal for a special scheme for treatment will be given.