Immunodeficiency-17 (IMD17) is an autosomal recessive primary immunodeficiency characterized by highly variable clinical severity. Some patients have onset of severe recurrent infections in early infancy that may be lethal, whereas others may be only mildly affected or essentially asymptomatic into young adulthood. More severely affected patients may have evidence of autoimmune disease or enteropathy. The immunologic pattern is similar among patients, showing partial T-cell lymphopenia, particularly of cytotoxic CD8 (see 186910)-positive cells, decreased amounts of the CD3 complex, and impaired proliferative responses to T-cell receptor (TCR)-dependent stimuli. B cells, natural killer (NK) cells, and immunoglobulins are usually normal. Although thymic output of functional naive T cells early in life is decreased, polyclonal expansion of functional memory T cells is substantial. The phenotype in some patients is reminiscent of severe combined immunodeficiency (SCID) (summary by Timon et al. (1993) and Recio et al. (2007)).

Immunodeficiency-18 is an autosomal recessive primary immunodeficiency characterized by onset in infancy or early childhood of recurrent infections. The severity is variable, encompassing both a mild immunodeficiency and severe combined immunodeficiency (SCID), resulting in early death without bone marrow transplantation in some patients. Immunologic work-up of the IMD18 SCID patients shows a T cell-negative, B cell-positive, natural killer (NK) cell-positive phenotype, whereas T-cell development is not impaired in the mild form of IMD18 (summary by de Saint Basile et al., 2004).

Immunodeficiency-65 (IMD65) is an autosomal recessive immunologic disorder characterized by onset of recurrent and severe viral infections from early infancy. Affected individuals have impaired ability to fight viral infections, resulting in clinically significant disease, including pneumonia, bronchiectasis, and septic shock. Laboratory studies may show lymphopenia or hypogammaglobulinemia, particularly during infection; more detailed studies show an impaired cellular type I interferon response. Treatment with intravenous immunoglobulin (IVIg) is beneficial. Important features of this disorder include the rapid development of septic shock, as well as poor outcomes after vaccination with live attenuated vaccines; such vaccines should never be administered to patients with known impaired interferon responses (summary by Hernandez et al., 2018 and Bravo Garcia-Morato et al., 2019).