Acute lymphocytic leukemia (ALL) in adults
ALL, the final of our quartet of leukemias. This is an acute malignancy affecting B or T lymphocyte cell lines, preventing them to mature effectively and promoting uncontrolled proliferation of immature blast cells with marrow failure and tissue infiltration. It is a rare condition, with 75% of cases occurring in children less than 6, the remaining 25% happen in the second peak of around 35 years of age.
The cause is unknown, but is thought to be a combination of genetic susceptibility (translocations, and gains and losses), with monozygotic twins having a 25% concordance. Environmental factors are thought to include radiation, smoking, infections and folate metabolism polymorphisms.
We can divide ALL based on three different systems:
- Based on morphology - uses microscopic appearance
- Based on immunological surface maersk (precursor B cell ALL, precursor T cell ALL)
- Based on cytogenetic - uses chromosomal analysis to divide based on chromosomal anomalies such as translocations
- The most common adult error is the philadelphia chromosome, t(9;22)
The pathogenesis is simple, genetic error leads to uncontrolled proliferation of lymphoid progenitor through a dysregulated process. These immature blast cells that are then created at a speedy rate infiltrate the bone marrow and other organs, disrupting their normal function and leading to the symptoms associated with ALL. As with other leukaemias, this is the product of clonal expansion of a single cell..
Common symptoms can be broken down based on their cause:
- Bone marrow failure - anaemia, infection, bleeding
- Infiltration - hepato and splenomegaly, lymphadenopathy - superficial or mediastinal, orchidomegaly, CNS involvement (e.g. cranial nerve palsies)
- Thymic masses are common in ALL, as are purpura and gingival hypertrophy so be aware
Do full barrage of tests, over 90% of patients will have clinically evident haematological abnormalities at the time of diagnosis. Normocytic normochromic anaemia with low reticulocyte count is present in 80% of patients, leukocytosis in 50%, 25% have a WBC greater than 50.000/microliter but with severe neutropenia. May also see increased calcium, potassium, phosphorus, uric acid and LDH. As with AML, >20% lymphoblasts seen on blood film or bone marrow aspirate is diagnostic of ALL.
Image: “Acute lymphoblastic leukemia” by Animalculist, CC BY-SA 4.0, via Wikimedia Commons.
Management is chemo, potentially with prophylactic intrathecal therapy to reduce the rate of CNS recurrence.