The origin of acute lymphoblastic leukemia (ALL) may be explained by a combination of genetic susceptibility and environmental exposure. We aimed to study the frequency of CYP1A1 allelic variants in Egyptian patients with ALL, to evaluate
their role in the development of ALL and to correlate these allelic variants with clinical and biological characteristics of the patients. Polymorphism of CYP1A1 * 2A , * 2B and * 4 alleles was examined in 186 Egyptian children with ALL and 200 normal individuals using polymerase chain reaction-single stranded conformation polymorphism (PCR-SSCP). A higher prevalence
of the CYP1A1 * 4 allele was found in patients with ALL than in the normal population (19.4%vs. 10.0%, odds ratio [OR]  2.160, 95% confidence interval [CI]  1.200 – 3.89, p  0.01), especially in the homozygous variant (OR  6.6, 95% CI  2.23 – 19.58,
p  0.001) and in male patients ( p  0.005), particularly those aged 2 – 10 years (OR  5.214, 95% CI  1.535 – 17.706, p  0.008).
CYP1A1 * 2A showed a significant difference between age groups ( p  0.046), with a higher incidence in the 10 – 17-year-old group
(21.1%). Multivariate analysis showed that only the CYP1A1 * 4 allele remained as a probable independent risk factor for ALL development (OR  2.250, 95% CI  1.244 – 4.069; p  0.007).
Our results suggest that polymorphic variants in the CYP1A1 * 4 gene may increase the risk of childhood ALL, particularly in male patients aged 2 – 10 years.