Management of XLP-1 and ITK deficiency: The challenges posed by PID with an unpredictable spectrum of disease manifestations

The incorporation of next generation sequencing into routine immunological practice has enabled the identification of novel inborn errors of disease, helped define new categories of immune deficiency and extended the clinical spectrum associated with many long-recognised diseases. The family of EBV (Epstein Barr Virus)-sensitive primary immune deficiencies is one such group and in this paper we describe three families: two with X-linked lymphoproliferative disease type-1 (XLP-1) and one with deficiency of Interleukin-2 Inducible T-cell Kinase (ITK). Both diseases have a wide range of clinical manifestations and are united by an exquisite predisposition to EBV, dysgammaglobulinemia, hemophagocytic lymphohistiocytosis, and lymphoma. We detail our approach to diagnosis, treatment, and risk stratification in these diseases where both clinicians and patients must grapple with constant uncertainty.