Introduction x-linked agarnmagobulinemia(XLA)1s a primary immunodeficiency disorder caused by Bruton’ s tyrosine kLnase (Btk) gene mutation Recent studies suggested genotype-phenotype correlation in XLA. but a definitiveassociation remains controversial. Patients and Methods We examined the relationship between specific Btk gene mutations and sevefitv of clmlcal presentation in 62 Patients with XLA Disease severity was assessed bythe age 0fdisease onsetandthe presence of severe infections, while mutations were classified into severe and mild based on structural and functional consequence by bininformatics analvsis Results Fifty six Btk mutations were identified in 62 patients from 57 kindreds Variation in phenotypes was observed, and there was a tendency of association between genotype and age of disease onset as well as occurrence of severe infections. Conclusion A critical analysis of the circumstances upon presentation also revealed that under-recognition of recurrent infections and relevant thmily history are important hurdles to timely diagnosis of XLA.