This is a multi-center trial for rasburicase in children at high risk of tumor lysis syndrome who have a history of asthma/atopy. The main purpose of this study is to establish the safety of this drug in patients with a history of asthma or severe allergies.

Because they were excluded from most of the clinical trials of non-recombinant urate oxidase and rasburicase, the safety of rasburicase in this population is not known, though preliminary data indicates that the drug is safe. The primary objective of this study is to estimate the proportion of grade 3 or 4 allergic reactions to rasburicase in patients with a history of asthma or severe allergy (to antigens other than rasburicase or other urate oxidases) treated with rasburicase for the prevention or treatment of malignancy or chemotherapy-induced hyperuricemia. Patients at risk of tumor lysis syndrome with a history of asthma/atopy will be treated with rasburicase according to standard practice and observed for allergic reactions.

Inclusion Criteria:

• A diagnosis of hematologic malignancy
• Existing hyperuricemia or high risk of developing hyperuricemia of malignancy
• The treating clinician plans to treat the patient with rasburicase. A patient is only eligible for RASALL if the clinician has already decided to use rasburicase. Rasburicase should not be given in order to make a patient eligible for this non-therapeutic observational study.
• No prior exposure to rasburicase or other urate oxidase
• A history of asthma or significant allergy

Exclusion Criteria

• Wheezing or an active hypersensitivity reaction at entry
• Hypersensitivity to Aspergillus proteins