Klinefelter syndrome is a condition in which a male patient has one Y chromosome 
and one or more extra X chromosomes. It is the most common sex chromosome 
disorder. Klinefelter syndrome is distinguished by many clinical features, such 
as infertility, high gonadotropin and low testosterone levels, increased height, 
and sparse body and facial hair. We report the case of a 32-year-old man who 
visited our hospital complaining of male infertility. Semen analysis showed 
azoospermia, and chromosomal analysis revealed a 47,XY,i(X)(q10) karyotype, 
which is a rare variant of Klinefelter syndrome. No spermatozoon was found on 
microdissection testicular sperm extraction, and the testis biopsy histology 
showed only Sertoli cells and hyalinised seminiferous tubules. 47,XY, i(X)(q10) 
has an additional isochromosome made of the long arm of the X chromosome, which 
shares some features of classical Klinefelter syndrome in many aspects, but 
patients are usually shorter than average height and have normal intelligence. 
In addition, to the best of our knowledge, no successful sperm extractions from 
47,XY, i(X)(q10) patients were reported in the literature. The reports of 
patients who have undergone microdissection testicular sperm extraction are very 
rare. Further reports and studies of this chromosomal abnormality are needed.