Neutralizing anti–type I interferon (IFN-α subtypes and IFN-ω) antibodies are highly specific, often present before clinical disease, and now serve as early diagnostic biomarkers; other antibodies (e.g., anti–IL-17/IL-22) explain susceptibility to candidiasis, while organ-specific targets (e.g., NALP5 in APS-1 hypoparathyroidism) can assist phenotypic classification and monitoring [33,35,37]. Here, IL17A is linked to autoimmune polyendocrine syndrome type 1.