PTPRN and type 1 diabetes mellitus: To conclude whether collections of autoantibodies, including those reactive to IA-2 autoantigen(s), may predict T1D, Pietropaolo and colleagues proposed in recent experiments [5] that autoantibodies against a combination of extracellular domain of IA-2 and/or conventional autoimmunity markers can distinguish between rapid and slow progressors of T1D.