The study of rare inherited disorders has led to an improved understanding of how the human immune system is regulated. This knowledge is necessary to develop new therapeutic agents to treat immunodeficiency, autoimmunity, cancer and transplantation. DOCK8 deficiency is one such illustrative disorder which, although only discovered in 2009, has already provided insight into the importance of DOCK8 in regulating the immune system to fight off infections, prevent allergic disease and avoid malignancies. This special issue of Disease Markers presents a collection of eight reviews on the subject of DOCK8 and related immunodeficiencies. Aspects covered include; the biochemical function of DOCK molecules, impaired antibody responses, the role of DOCK molecules in cell trafficking, comparisons between hyper-IgE syndrome due to STAT3, TYK2 and DOCK8 mutations, as well as a number of other related disorders. Together these eight reviews provide a background picture of this fascinating area of human immunodeficiency and identify important areas for future research.