Fig. 1.

Schematic overview of the mutational mechanisms and effects on gene, protein, and pathway level with the phenotypic manifestations that result from various forms of PID. For autosomal recessive, X-linked and autosomal dominant forms of PID, the effects on the gene level and subsequently on the protein level are indicated that lead to either deficiency or hyperactivation of the immunological pathways involved. These effects at the pathway level can either result in a phenotype manifesting with symptoms of immunodeficiency, autoimmunity, or autoinflammation. Pathogen exposure can be a prerequisite for the phenotype to develop, which contributes to the incomplete penetrance observed in PIDs.