Kuhns, Douglas B.

Humans with monogenic inborn errors responsible for extreme disease phenotypes can reveal essential physiological pathways. We investigated germline mutations in GNAI2 , which encodes G αi2 , a key component in heterotrimeric G protein signal transduction usually thought to regulate adenylyl cyclase–mediated cyclic adenosine monophosphate (cAMP) production. Patients with activating G αi2 mutations had clinical presentations that included impaired immunity. Mutant G αi2 impaired cell migration and augmented responses to T cell receptor (TCR) stimulation. We found that mutant G αi2 influenced TCR signaling by sequestering the guanosine triphosphatase (GTPase)–activating protein RASA2, thereby promoting RAS activation and increasing downstream extracellular signal–regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)–AKT S6 signaling to drive cellular growth and proliferation.

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).