Rare Daily Staff

Addi and Cassi Hempel, twin girls with the rare genetic condition Niemann-Pick type C who grew prominent in the rare disease community through their parents’ efforts to advance a potential treatment for their condition, died July 4 from lung infections, according to a Facebook post from their parents. They were 14.

“The twins both came down with a severe respiratory virus over the weekend which landed them in the hospital for oxygen support,” their mother Chris Hempel wrote in a Facebook post. “This flu took over their fragile lungs like a storm.”

In 2007, at the age of 3 the twins were diagnosed with Niemann-Pick type C (NPC), an ultra-rare lysosomal storage disorder that results from the accumulation of lipids in cells and organs throughout the body including the spleen, liver, lungs, and brain. It causes progressive neurological deterioration with symptoms including dementia, seizures, ataxia and cataplexy.

The Hempels’ quest to find a treatment for their daughters has been well documented in press accounts. They created a virtual biotech and won U.S. Food and Drug permission to administer 2-hydroxypropyl-β-cyclodextrin to the girls. Cyclodextrin is a non-toxic sugar compound added to many fat free food products. They were the first children to receive the experimental treatment.

The treatment is the subject of late-stage clinical studies by Mallinckrodt Pharmaceuticals, which acquired the therapy from Sucampo after it purchased Vtesse. But the Hempels brought suit in 2018 in the United States District Court in Nevada against the rare disease accelerator Cydan, Vtesse, and Sucampo alleging breach of contract and misappropriation of trade secrets.

“Chris and I are so incredibly sad but also grateful for all that the twins gave to us and gave to so many others… They were so brave and so full of love,” wrote the girls’ father Hugh Hempel. “As one of our friends said yesterday, ‘They came into the world together, journeyed together, and left together.’ That is so true. They were and will always be the epitome of soulmates.”

The Hempels said they plan to hold a celebration of the girls’ lives at their home in Reno, Nevada later this summer.

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