INTRODUCTION: The variable number of tandem repeats (VNTR) of the dopamine 
receptor D4 (DRD4) gene among humans may elucidate individual differences in 
susceptibility to neuropsychiatric diseases. Dopamine dysfunction may be 
involved with Attention Deficit Hyperactivity Disorder (ADHD) symptoms. In this 
study, we report the association between the phenotype of ADHD, a condition 
characterized by inattentiveness, hyperactivity, and impulsiveness, and a 
48-base pair VNTR in exon 3 of the DRD4 polymorphism.
SUBJECTS AND METHODS: We used a case control approach conducted on 29 ADHD and 
31 ethnically matched control Egyptian children (ages 6-12 years). Cases were 
assessed by a psychiatric semi-structured interview and the Conners' Parent 
Rating Scale. VNTR polymorphisms of the DRD4 gene were done by touchdown PCR 
program using exon 3-specific primers followed by agarose gel electrophoresis.
RESULTS: We observed a significant association between the existence of D4.4 
allele of DRD4 and ADHD (P, 0.002); 6.9% of cases showed a single D4.4 and 10.3% 
showed a double D4.4 as compared to controls in whom D4.4 has never been 
detected.
CONCLUSION: Children with smaller number of repeat alleles (two to four repeats) 
of the DRD4 gene have higher possibility to develop ADHD in Egyptian children.