Procainamide-induced agranulocytosis with reversible myeloid sensitivity

Area of Science:

• Hematology
• Pharmacology
• Toxicology

Background:

• Agranulocytosis is a severe adverse drug reaction characterized by a significant reduction in neutrophils.
• Procainamide, an antiarrhythmic drug, is a known potential cause of agranulocytosis.
• Understanding the mechanisms of drug-induced bone marrow suppression is crucial for patient safety.

Observation:

• A 56-year-old male presented with procainamide-induced agranulocytosis.
• Bone marrow examination revealed a critical lack of myeloid cells beyond the promyelocyte stage.
• In vitro studies demonstrated that procainamide suppressed bone marrow granulocyte-macrophage colony-forming units (CFUc) growth.

Findings:

• Procainamide exposure directly inhibited CFUc growth in the affected patient's bone marrow.
• CFUc growth normalized in the absence of the drug.
• Following clinical recovery, the patient's bone marrow CFUc demonstrated no sensitivity to procainamide in vitro.

Implications:

• This case highlights a unique instance of reversible drug sensitivity in procainamide-induced agranulocytosis.
• Contrasts with other reported cases showing persistent bone marrow injury or drug sensitivity post-recovery.
• Suggests variable individual responses to drug-induced hematotoxicity, impacting treatment and prognosis.