75‐year‐old lady with a background of rheumatoid arthritis, for which she takes methotrexate. She has been more tired than normal in the last few months, with some mild lower back pain. She has not lost weight and nor has she had any night sweats. Recent blood taken as part of her methotrexate monitoring show mild normocytic anaemia (Hb 105), with normal U&Es and LFTs. You feel this is most likely anaemia of chronic disease, but you want to order some further investigations to rule out more serious conditions: iron studies, B12 and folate, LDH, bone profile, a blood film and myeloma screen. The gene discussed is GSTM1; the disease is anemia (phenotype).