High Incidence of Severe Combined Immune Deficiency in the Eastern Province of Saudi Arabia

Severe combined immunodeficiency (SCID) is a group of rare genetic disorders with an estimated incidence of 1 in 50,000 to 1 in 500,000 live births, invariably fatal in early infancy if not corrected. In the period 1990–2002 we diagnosed 18 cases of SCID in 11 Saudi Arab families at our hospital, which serves a population of 250,000 in the eastern province of Saudi Arabia. During the same period there were 90,555 live births. Of the 18 cases of SCID, 7 children survived, 6 after HLA identical fully matched bone marrow transplantation from siblings, 1 child with adenosine deaminase deficiency (ADA) surviving on ADA replacement. The other 11 patients died from serious infections. The incidence of SCID in our population is 19 per 100,000 live births, the highest incidence reported in the world. Most of our cases are autosomal recessive, and the product of consanguineous marriage. If we exclude the minor immunoglobulin (Ig)A and IgG subclass deficiencies, SCID represents 50% of all serious primary immunodefic...