Ataxia-telangiectasia (AT) is an autosomal recessive disorder, characterized by cerebellar ataxia, oculo-cutaneous telangiectasia, progressive impairment of immune and neurological systems, chromosomal instability, increased radiosensitivity, and a propensity to develop cancer and lymphoma (Gatti, 1995). We report the case of a female patient with AT, who developed B-cell non-Hodgkin's lymphoma (NHL), successfully treated with modified CHOP chemotherapy (cyclophosphamide, hydroxydoxorubicin, vincristine and prednisone) plus Rituximab. At 17 years of age, she was diagnosed with stage IV-B, diffuse large B-cell lymphoma (DLBCL), originating from the left maxillary sinus. Magnetic resonance imaging (MRI) of the head revealed the presence of a maxillary sinus mass, with local bone erosion (Fig 1A). Chest radiography and ultrasonography detected neither mediastinal nor abdominal localization. Lytic bone lesions were observed in the pelvis. Bone marrow aspirate was normal. Nasal biopsy performed by fibroendoscopy revealed DLBCL of the centroblastic variety. Lymphoma cells were positive for CD45, CD79 and CD20; integrated Epstein–Barr virus (EBV) DNA was absent. (A) MRI of the head at time of diagnosis, showing the presence of a left maxillary sinus mass involving the homolateral ethmoidal cavity with local bone erosion. (B) Repeat MRI of the head conducted following eight cycles of CHOP plus Rituximab. The image shows the resolution of the primary mass and evidence of local bone healing. Chemotherapy was considered and, in order to avoid the severe complications reported in patients with AT treated for cancer (Abadir & Hakamin, 1983), a modified dosage of CHOP was chosen. The patient received: cyclophosphamide 300 mg/m2, doxorubicin 15 mg/m2, vincristine 1 mg/m2 on d 1, prednisone 40 mg/m2/d for 5 d. This treatment was repeated every 3 weeks for eight cycles. On d 2 of each cycle, the addition of Rituximab at a dosage of 375 mg/m2 was made. No side-effects were observed after Rituximab infusion. Radiation therapy was not employed. Complete remission of primary mass was achieved (Fig 1B); lytic bone lesions of the pelvis also disappeared. Follow-up, performed every 4 months by periodic MRI and gallium radionuclide scanning, remained negative. Cardiorespiratory functional tests after chemotherapy remained normal. Neither any further detectable neurological deterioration nor the development of any life-threatening infectious complications were observed. Twenty-four months after diagnosis of DLBCL, the patient continued to be in complete remission. Increased chromosomal fragility and impaired repair of chromosomal damage have been implicated in the pathogenesis of cancer in patients with AT. Because of these defects, radiotherapy and chemotherapy should be used with caution in the treatment of malignancies arising in AT patients (Abadir & Hakamin, 1983). In fact, several investigators have noted severe toxic effects after standard polychemotherapy, which can lead to the development of lethal complications (Weyl Ben Arush et al, 1995). The treatment of AT-associated lymphoid malignancies must take into account these observations and deliver an adequate dose of chemotherapeutic drugs in order to destroy the tumour burden without undue toxic effects; such tailoring of treatment remains a major clinical challenge. On the other hand, Sandoval and Swift (1998) showed that reduced chemotherapy was associated with both a lower remission rate and worse median survival when compared with standard chemotherapy. The use of chemotherapeutic agents that are directly associated with a monoclonal antibody specifically targeted to tumour cells may allow the delivery of effective anti-tumour therapy with a reduced dosage of cytotoxic agents and thus lessen chemotherapy-associated side-effects. Rituximab is a chimaeric monoclonal antibody against CD20, a surface antigen present in all patients with NHL originating from B cells. When associated with modified CHOP, Rituximab has been shown to be both active and effective for the treatment of elderly patients with diffuse large B-cell lymphoma, without incurring a clinically significant increase in toxicity when compared with CHOP alone (Coiffier et al, 2002). Moreover, the efficacy of Rituximab has been proven for the treatment of post-transplant lymphoproliferative disease (PTLD), which is a paradigm of lymphoid proliferative disorders originating from immunodeficiency-related conditions (Cook et al, 1999). The favourable response observed and the absence of side-effects in response to Rituximab administration suggests that Rituximab, in combination with reduced-dosage CHOP, may improve the outcome of aggressive B-cell lymphoma treatment when presented as a complication of AT. This work has been partly supported by grants from AIRC (Associazione Italiana Ricerca sul Cancro), CNR (Consiglio Nazionale delle Ricerche), MURST (Ministero dell'Università e della Ricerca Scientifica e Tecnologica) and IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico) Policlinico S. Matteo to F.L.