Fever for 3-5 days without any symptoms for a 6 year old boy almost every month . what could be the reason ?

Fever: You child may have periodic febrile syndrome or familial meditranean syndrome common in middle eastern subjects which is caused by a genetic defect. Further study is necessary.

FEVER: Keep temperature chart. Check with his pediatrician during a febrile episode for a detailed history about type, pattern, duration, relief of fever, etc; a complete physical exam. His pediatrician might ask for some labs done during the febrile episode.