Antiproliferative actions on bone marrow and GI tissue: Due to the drugs preference for rapidly proliferating tissues, bone marrow depression (anemia, leukopenia, pancytopenia, or even rarely agranulocytosis) may occur. Aplastic anemia has also been seen. Bone marrow toxicity can be irreversible and may cause death, particularly in immunocompromised patients. GI toxicity may be severe or rarely fatal and consists of anorexia, abdominal bloating, abdominal pain, diarrhea, dry mouth, duodenal ulcer, GI hemorrhage, nausea, vomiting, and ulcerative colitis. Liver function: Elevations of liver enzymes and bilirubin, hepatic dysfunction, jaundice and, in one patient, liver necrosis have all been seen. Some fatal cases have been reported; however, the majority of cases was reversible. Renal function: Increased BUN and serum creatinine have been noted. Crystalluria (formation of crystals and excretion in the urine) and acute kidney injury have also been seen. Adverse central nervous system effects are frequent and include confusion, hallucinations, psychosis, ataxia, hearing loss, headache, paresthesia, parkinsonism, peripheral neuropathy, vertigo and sedation. Skin reactions: Rash, pruritus, and photosensitivity have all been noticed. Toxic epidermal necrolysis (Lyells syndrome) may also be encountered and may be life-threatening. Anaphylaxis: Sometimes cases of anaphylaxis consisting of diffuse erythema, pruritus, conjunctival injection, fever, abdominal pain, edema, hypotension and bronchospastic reactions are observed.It is not known if flucytosine is a human carcinogen. The issue has been raised because traces of 5-fluorouracil, which is a known carcinogen, are found in the colon resulting from the metabolization of flucytosine.
Lymphoid leukemias are a group of leukemias affecting circulating lymphocytes, a type of white blood cell. The lymphocytic leukemias are closely related to lymphomas of the lymphocytes, to the point that some of them are unitary disease entities that can be called by either name (for example, adult T-cell leukemia/lymphoma). Such diseases are all lymphoproliferative disorders. Most lymphoid leukemias involve a particular subtype of lymphocytes, the B cells. Classification
Historically, they have been most commonly divided by the stage of maturation at which the clonal (neoplastic) lymphoid population stopped maturing:
Acute lymphoblastic leukemia
Chronic lymphocytic leukemiaHowever, the influential WHO Classification (published in 2001) emphasized a greater emphasis on cell lineage. To this end, lymphoid leukemias can also be divided by the type of cells affected:

B-cell leukemia
T-cell leukemia
NK-cell leukemiaThe most common type of lymphoid leukemia is B-cell chronic lymphocytic leukemia. B-cell leukemias
B-cell leukemia describes several different types of lymphoid leukemia which affect B cells. Other types include (with ICD-O code):

9826/3 – Acute lymphoblastic leukemia, mature B-cell type
9833/3 – B-cell prolymphocytic leukemia
9940/3 – Hairy cell leukemia

T-cell leukemias
T-cell leukemia describes several different types of lymphoid leukemias which affect T cells.The most common T-cell leukemia is precursor T-cell lymphoblastic leukemia. It causes 15% of acute leukemias in childhood, and also 40% of lymphomas in childhood. It is most common in adolescent males. Its morphology is identical to that of precursor B-cell lymphoblastic leukemia. Cell markers include TdT, CD2, CD7. It often presents as a mediastinal mass because of involvement of the thymus.