Rare Genetic Condition Makes Woman Her Own Twin

A California woman has what appears to be a normal birthmark on her stomach. But the mark is actually the result of a rare genetic disorder that essentially makes the woman her own twin. 

The disorder, called chimerism, means the woman, Taylor Muhl, has two completely different sets of DNA inside her body. The phenomenon originated in the womb, where, as a developing fetus, Muhl absorbed her fraternal twin. That event created her two different colors of skin pigmentation split evenly down her midsection, as seen in the photo below.

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“I actually felt relief. I felt freedom because for the first time in my life I knew why my stomach looks the way it does,” Muhl, who learned about her condition about a decade ago but didn’t make the news public until last year, told People. “I felt like for the first time I could really breathe. Prior to that, every doctor said my stomach must have just been a birthmark.… Finally, this is making some sense.”

Muhl’s condition has brought her various health issues, including autoimmune complications and sensitivities to foods, medications, supplements, jewelry and insect bites, she wrote on her website. In addition, she has acid reflux, neuropathy, borderline fibromyalgia and endometriosis, according to Women’s Health.

“My body treats my sibling’s genetic makeup as foreign matter and wants to reject it—but can’t. It strips my immune system daily. Stress and lack of sleep makes things more severe,” she told Women's Health.

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The condition is extremely rare, and there’s “only 100 cases documented in the world at this time,” Muhl wrote on Instagram. There’s likely more people that have chimerism, but it probably goes undiagnosed, Dr. Brocha Tarshish, a clinical geneticist at Nicklaus Children’s Hospital, who has not treated the young woman, told Live Science.

Muhl isn’t the first person to make headlines for her disorder. In 2014, a DNA test revealed that Lydia Fairchild, a Washington mother with three children, didn’t carry the same DNA as her kids, The Philadelphia Inquirer reported. Turns out, chimerism was responsible for the genetic differences.