ADA and triple-A syndrome: The serum concentration of ADA at the point of AAA appearance in 16 patients was less than 0.1 μg/ml in six patients and 0.6–14.1 μg/ml in other ten patients; the levels were significantly low as compared with the trough concentration of 13.2 ± 9.2 μg/ml (mean ± SD) in 37 patients negative for AAA (P < 0.0001).