Pancytopenia and colitis with Clostridium difficile in a rheumatoid arthritis patient taking methotrexate, antibiotics and non-steroidal anti-inflammatory drugs.

Methotrexate (MTX) is widely used despite its side-effects. We describe a rheumatoid arthritis (RA) patient taking low-dose MTX who developed severe pancytopenia and colitis with Clostridium difficile after the administration of antibiotics for acute pyelonephritis. Our case suggests that low-dose MTX may seriously interact with antibiotics and that these side-effects should always be considered when RA patients are treated with MTX and antibiotics.