ObjectiveTo describe a 41‐year‐old woman with a history of neonatal onset multisystem inflammatory disease, on treatment with daily subcutaneous injections of 600 mg of recombinant interleukin‐1 receptor antagonist (IL‐1Ra) protein, anakinra, since the age of 28, who presented with golf‐ball size nodules at the anakinra injection sites, early satiety, new onset nephrotic syndrome in the context of normal markers of systemic inflammation.MethodsClinical history and histologic evaluation of biopsies of skin, gastric mucosa, and kidney with Congo‐red staining and proteomic evaluation of microdissected Congo red–positive amyloid deposits by liquid chromatography‐tandem mass spectrometry.ResultsThe skin, stomach, and kidney biopsies all showed the presence of Congo red–positive amyloid deposits. Mass spectrometry‐based proteomics demonstrated that the amyloid deposits in all sites were of AIL1RAP (IL‐1Ra protein)‐type. These were characterized by high spectral counts of the amyloid signature proteins (apolipoprotein AIV, apolipoprotein E, and serum amyloid P‐component) and the amyloidogenic IL‐1Ra protein, which were present in Congo red–positive areas and absent in Congo red–negative areas. The amino acid sequence identified by mass spectrometry confirmed that the amyloid precursor protein was recombinant IL‐1Ra (anakinra) and not endogenous wild‐type IL‐1Ra.ConclusionThis is the first report of iatrogenic systemic amyloidosis due to an injectable protein drug, which was caused by recombinant IL1Ra (anakinra).