We sequenced MKRN3, the major causative gene of central precocious puberty in Western countries, in 24 Japanese or Chinese patients and examined the DNA methylation and copy-number statuses of this gene in 19 patients. We identified no (epi)genetic defects except for one previously reported mutation. These results, together with reports from Korea, indicate that MKRN3 defects are rare in Asian populations. The ethnic differences likely reflect Western country-specific founder mutations and the rarity of de novo mutations.