Why Kim Jong Un went missing

(CNN) -- North Korean leader Kim Jong Un, who recently disappeared from public view for about six weeks, had a cyst removed from his right ankle, a lawmaker told CNN.

South Korea's National Intelligence Service told lawmakers during a closed-door meeting that a cyst was found on Kim's right ankle earlier this year, between May and June. That cyst may have caused muscle or nerve damage and prompted him to have ankle surgery between September and October, lawmaker Lee Cheol-woo said.

At the briefing, lawmakers were told that "European experts" handled the surgery for tarsal tunnel syndrome. The syndrome is caused by compression at the ankle -- known to cause pain during standing and walking.

Kim is believed to be recovering, South Korean lawmakers were told, but the cyst could recur due to his obesity and heavy schedule.

After his conspicuous absence throughout most of September, Kim seemed to reappear October 14, when North Korean state media published the first photos of him, in which the beaming Kim held a cane in his left hand as he gave "field guidance" at a newly built residential district.

Kim hadn't been seen in public since he reportedly attended a concert with his wife on September 3. It was his longest absence from official events since he made his first public appearance in 2010, according to NK News, a website devoted to analyzing North Korea.

South Korean lawmakers also were told that a political purge continues in North Korea, as a follow-up after the execution of Kim's uncle, Jang Song Thaek. North Korea executed 10 party officials by firing squad for charges ranging from corruption to women's issues to the viewing of a South Korean soap opera. Intelligence officials also told lawmakers that senior military officials were demoted for poor accuracy in artillery drills.

He skipped important anniversary

Before his disappearance, Kim was seen limping, prompting theories he was suffering everything from weight gain to gout. His sudden disappearance took aconcerning turn earlier this month when he didn't appear at events to mark the 65th anniversary of the Worker's Party of North Korea.

Kim's failure to appear fueled rampant speculation.

Since his reappearance, North Korea has released several photos of Kim, but has yet to release video.

According to Dr. Kim So-Yeon, the former personal doctor to Kim's grandfather Kim Il Sung, Kim inherited a number of health issues, including psychological problems and a history of obesity. She said both Kim Il Sung and Kim's father, Kim Jong Il, suffered from diabetes, heart problems and stress.

After studying the photos, she said Kim's face appeared to have swollen due to painkillers. She also speculated that he has been receiving hormone shots to make him look more like his grandfather, the much-revered founder of North Korea.