Autosomal recessive disorder due to deficiency of lymphocyte-specific protein-tyrosine kinase (Lck or p56lck), one of the proteins activated upon engagement of the TCR/CD3 complex. Depending on the mutation, individuals may present within the first year of life with variable features.

Kabuki syndrome is a multisystem genetic disorder involving characteristic facial features, growth and developmental delay, and skeletal abnormalities.

Deficiencies of the cytokine, IL-21, and IL21 receptor has been described in children with very early onset inflammatory bowel disease, liver disease, and immunodeficiency with T cell and B cell defects.

Short for immunodeficiency-centromeric instability facial anomalies syndrome, ICF syndrome is an autosomal recessive disorder that may be due to variants in the ZBTB24, DNMT3B, CDCA7, or HELLS genes.

Individuals with this condition can present with severe T cell defects that may mimic severe combined immunodeficiency (SCID) at birth. Additionally, they present with significant bone deformities, such as early fused cranial bones (craniosynostosis) with a small cervical canal, short stature, and abnormally shaped digits.

DOCK2 deficiency is an autosomal recessive disorder associated with early-onset invasive bacterial and viral infections, lymphopenia, and defective T, B, and NK cell function.

Coronin 1A deficiency is associated with a very low number of T cells with impaired function, similar to severe combined immunodeficiency (SCID).

Combined immunodeficiency with intestinal atresias (CID-IA) is a rare, severe disorder in which parts of the small intestine fail to develop properly.

CD8 deficiency is an extremely rare autosomal recessive disorder due to homozygous mutation of CD8 gene.

CD70 deficiency is a rare form of combined immunodeficiency with hypogammaglobulinemia and low CD8+ T cells. Individuals are particularly susceptible to chronic Epstein-Barr virus (EBV) and at high risk of EBV-associated lymphoma.