The co‐occurrence of Wilson disease and X‐linked agammaglobulinemia in one family highlights the promising diagnostic potential of proteolytic analysis

BACKGROUND: We report the first case of a family with co‐occurrence of Wilson disease (WD), an autosomal recessive disorder of copper metabolism, and X‐linked agammaglobulinemia (XLA), a primary immunodeficiency disorder (PIDD) that features marked reduction in circulating B lymphocytes and serum immunoglobulins. METHODS AND RESULTS: Through utilization of a multiplexed biomarker peptide quantification method known as the immuno‐SRM assay, we were able to simultaneously and independently identify which family members are affected with WD and which are affected with XLA using dried blood spots (DBS). CONCLUSION: Being able to delineate multiple diagnoses using proteolytic analysis from a single DBS provides support for implementation of this methodology for clinical diagnostic use as well as large‐scale population screening, such as newborn screening (NBS). This could allow for early identification and treatment of affected individuals with WD or XLA, which have been shown to reduce morbidity and decrease mortality in these two populations.