T-cell immunodeficiency with thymic aplasia (TIDTA) is an autosomal recessive disorder that is often detected at birth through newborn SCID screening with the finding of decreased T-cell receptor excision circles (TRECs). Affected individuals have selective hypo- or aplasia of the thymus, which results in T-cell immunodeficiency due to impaired T-cell development and increased susceptibility to viral infections. The phenotype is similar to T-/B+/NK+ SCID. Some patients may die in childhood; thymus transplantation may be curative (summary by Du et al., 2019).

Autoimmune lymphoproliferative syndrome (ALPS), caused by defective lymphocyte homeostasis, is characterized by the following: Non-malignant lymphoproliferation (lymphadenopathy, hepatosplenomegaly with or without hypersplenism) that often improves with age. Autoimmune disease, mostly directed toward blood cells. Lifelong increased risk for both Hodgkin and non-Hodgkin lymphoma. In ALPS-FAS (the most common and best-characterized type of ALPS, associated with heterozygous germline pathogenic variants in FAS), non-malignant lymphoproliferation typically manifests in the first years of life, inexplicably waxes and wanes, and then often decreases without treatment in the second decade of life; in many affected individuals, however, neither splenomegaly nor the overall expansion of lymphocyte subsets in peripheral blood decreases. Although autoimmunity is often not present at the time of diagnosis or at the time of the most extensive lymphoproliferation, autoantibodies can be detected before autoimmune disease manifests clinically. In ALPS-FAS caused by homozygous or compound heterozygous (biallelic) pathogenic variants in FAS, severe lymphoproliferation occurs before, at, or shortly after birth, and usually results in death at an early age. ALPS-sFAS, resulting from somatic FAS pathogenic variants in selected cell populations, notably the alpha/beta double-negative T cells (a/ß-DNT cells), appears to be similar to ALPS-FAS resulting from heterozygous germline pathogenic variants in FAS, although lower incidence of splenectomy and lower lymphocyte counts have been reported in ALPS-sFAS and no cases of lymphoma have yet been published.

Autoimmune lymphoproliferative syndrome (ALPS), caused by defective lymphocyte homeostasis, is characterized by the following: Non-malignant lymphoproliferation (lymphadenopathy, hepatosplenomegaly with or without hypersplenism) that often improves with age. Autoimmune disease, mostly directed toward blood cells. Lifelong increased risk for both Hodgkin and non-Hodgkin lymphoma. In ALPS-FAS (the most common and best-characterized type of ALPS, associated with heterozygous germline pathogenic variants in FAS), non-malignant lymphoproliferation typically manifests in the first years of life, inexplicably waxes and wanes, and then often decreases without treatment in the second decade of life; in many affected individuals, however, neither splenomegaly nor the overall expansion of lymphocyte subsets in peripheral blood decreases. Although autoimmunity is often not present at the time of diagnosis or at the time of the most extensive lymphoproliferation, autoantibodies can be detected before autoimmune disease manifests clinically. In ALPS-FAS caused by homozygous or compound heterozygous (biallelic) pathogenic variants in FAS, severe lymphoproliferation occurs before, at, or shortly after birth, and usually results in death at an early age. ALPS-sFAS, resulting from somatic FAS pathogenic variants in selected cell populations, notably the alpha/beta double-negative T cells (a/ß-DNT cells), appears to be similar to ALPS-FAS resulting from heterozygous germline pathogenic variants in FAS, although lower incidence of splenectomy and lower lymphocyte counts have been reported in ALPS-sFAS and no cases of lymphoma have yet been published.

Griscelli syndrome type 2 (GS2) is an autosomal recessive disorder characterized by pigmentary dilution of the skin and hair, the presence of large clumps of pigment in hair shafts, and an accumulation of melanosomes in melanocytes. Patients also have immunologic abnormalities with or without neurologic impairment (summary by Menasche et al., 2000). Some GS2 patients have been reported in whom central nervous system manifestations are the first presentation (Rajadhyax et al., 2007, Masri et al., 2008; Mishra et al., 2014; Lee et al., 2017). For a discussion of phenotypic and genetic heterogeneity of Griscelli syndrome, see Griscelli syndrome type 1 (GS1; 214450).

LICS is an autosomal recessive chromosome breakage syndrome characterized by failure to thrive in infancy, immune deficiency, and fatal progressive pediatric lung disease induced by viral infection. Some patients may have mild dysmorphic features (summary by van der Crabben et al., 2016).