Identical 3250-bp deletion between two AluI repeats in the ADA genes of unrelated ADA−SCID patients

Abstract Recently, we investigated a Belgian patient with severe combined immune deficiency caused by a dysfunction of the gene for adenosine deaminase (ADA − SCID), which was found to be due to a 3.2-kb deletion spanning the promoter and the first exon of the ADA gene (Berkvens et al. , 1987, Eur. J. Pediatr. 146: 329). No ADA-specific RNA could be detected in primary fibroblasts derived from this patient. In the present paper we establish via direct sequencing of in vitro amplified DNA that the 3250-bp deletion is due to a recombination within the left arms of two direct Alu I repeats. This mutation is identical to one reported for an unrelated patient in the United States (Markert et al. , 1988, J. Clin. Invest. 81: 1323–1327).