Table 2.

Retrospective studies that show variation according to geographical differences.

Author	Year	Number of cases	Country	Idiopathic	Infection
Carlos et al. [6]	2000	106 patients (82 females)	Spain	35%	34%
Psychos et al.[3]	2000	110 females	Greece	35%	17.3%
Tay [7]	2000	75 patients (65 females)	Singapore	60%	29%
Puavilai et al.[8]	1995	100 patients (88 females)	Thailand	72%	18%