Confidentiality agreements can also make patients think twice before talking about P.A.H. even with friends — let alone on social media, an important forum for sharing such information, said Dr. Rita Redberg, a cardiologist at the University of California, San Francisco, who studies the regulatory process for medical devices.

A Supermodel Sues

In 2021, Ms. Evangelista, one of the most recognizable supermodels of the 1980s and ’90s, said she had gone into a long seclusion after developing P.A.H. She sued Zeltiq and announced last summer that she had settled with the company. Ms. Evangelista declined to comment for this article.

The year she went public, the F.D.A. received over 1,100 reports of adverse events from CoolSculpting treatments — more than in the entire previous decade. Last year, the agency received more than 1,900. A majority of all the reports refer to hyperplasia.

Ms. Kinard said the spike, which she believes can be attributed in part to Ms. Evangelista, is “alarming because the device has been around for many years.”

Ms. D’Addario, who reported her condition to the F.D.A., said that before she knew what P.A.H. was, she would work out constantly, trying to lose the fat that had emerged after CoolSculpting. Now, years later, she said, she understands that it was not her fault.

But the “mental trauma” from the mysterious ways her body became deformed, and the months of not knowing what was happening, remain with her, she said: “I’m struggling now to this day. Probably worse.”

Christina Jewett and Valeriya Safronova contributed reporting.

Research was contributed by Sheelagh McNeill, Kitty Bennett, Alain Delaquérière, Kirsten Noyes and Jack Begg.