Immune basis for cimetidine-induced pancytopenia

Area of Science:

• Hematology
• Immunology
• Pharmacology

Background:

• Chronic myelogenous leukemia (CML) is a myeloproliferative neoplasm.
• Accelerated phase CML can present with pancytopenia, encephalopathy, and myalgia.
• Cimetidine is a histamine H2 receptor antagonist used to treat acid reflux and ulcers.

Observation:

• A female CML patient, 8 years post-diagnosis, presented with pancytopenia, encephalopathy, and myalgia.
• The patient had been receiving cimetidine for 7 months.
• Initial diagnosis was suspected accelerated phase CML.

Findings:

• Discontinuation of cimetidine led to bone marrow recovery and resolution of myalgia and encephalopathy.
• Immunological studies revealed cimetidine stimulated lymphocyte blastogenesis.
• Incubation with cimetidine increased cytotoxic/suppressor T lymphocytes, indicating a cell-mediated immune response.

Implications:

• Cimetidine can induce pancytopenia through a cell-mediated immune mechanism.
• This case highlights the importance of considering drug-induced immune reactions in patients with hematological malignancies.
• Awareness of potential cimetidine-induced toxicity is crucial for patient management.