A severe combined immunodeficiency that is an autosomal recessive disease with T and B lymphocyte dysfunction, due to a large deletion at one allelle and a point mutation at the other. The point mutation resulted in the alteration of intervening sequence 13 donor splice site. The population of T lymphocytes is diminished and unresponsive to mitogen stimulation. The level of B lymphocyte numbers, serum immunoglobulin decreased with age.