MYSM1 and lymphopenia: Homozygous missense mutation of MYSM1, which is the catalytic site within the DUB (JAMM)/MPN domain, has been associated with complete absence of B lymphocytes, T cell lymphopenia, defective hematopoiesis, and developmental abnormalities, which further supports the essential role of MYSM1 in human hematopoietic development [125].