The creator and star of Girls posted a message on Instagram in response to the posting of a photo of paparazzi showing him walking with a cane.
"This is what life looks like when I struggle with the most chronic illness," she wrote. "The outburst of Ehler-Danlos Syndrome means I need the support of more than my friends … so thank you, sweet cane!"
"For years, I resisted doing anything that would alleviate my physical condition, insisting that a cane "would do things weird," she wrote. "But it's actually less strange to participate than to be in bed all day. And yes, you'd better believe I'm wearing my nightgown. I walked four feet to the car to go to the doctor and wanted to be utterly cozy. "
She was able to joke.
"I could lie and say it was an early look at Halloween (Don't you understand it? Florida Kees prison after being acquitted of killing her husband and now trying to get disability registration plates.) "
Dunham is the second celebrity in a month to reveal they have Ehlers-Danlos Syndrome.
Ehlers-Danlos Syndrome is a group of diseases that affect the connective tissues that support the skin, bones, blood vessels and other organs and tissues, according to the Na National Institute of Health Library. Many people with this condition have soft, brittle skin and bruises and scars easily.
CNN's Amir Vera contributed to this report.