Rheumatoid arthritis (RA), inflammatory bowel disease (IBD), psoriasis (PsO)+/−arthritis (PsA), ankylosing spondylitis (AS) and systemic lupus erythematosus (SLE) affect over 4% of adults and are usually treated with immune-suppressing drugs such as methotrexate (MTX), azathioprine (AZA) and anti-tumour necrosis factor (TNF)-alpha.1–6 Although effective, these medicines can cause drug-induced hepatitis, acute kidney injury and/or cytopenia. The gene discussed is TNF; the disease is systemic lupus erythematosus.