The star, 33, confessed she was "struggling" in the pictures, in which she's seen sporting a long blue nightie, slippers and grey cardigan.
Ehlers-Danlos syndrome is an inherited condition that affects the skin, joints, bones and organs.
Dunham wrote on Instagram: "I could choose to be embarrassed by these paparazzi pics — I mean, that’s probably the point of someone publishing them in the first place— but I’m really not.
"I could lie and say it was an early Halloween look (Don’t you get it? I’m going as a con woman leaving a Florida Keys jail after being acquitted of murdering her husband, and now she’s trying to get disability license plates.)
"But the truth is just: This is what life is like when I’m struggling most with chronic illness.
"An Ehler-Danlos syndrome flare means that I need support from more than just my friends... so thank you, sweet cane!
"For years, I resisted doing anything that would make my physical situation easier, insisting that a cane would 'make things weird'.
"But it’s so much less weird to actually be able to participate than to stay in bed all day.
"And yes, you'd better believe I'm wearing my nightgown.
"I was walking four feet to the car to go to the doctor and I wanted to be full cozy. I mean, didn't Bieber wear hotel slippers for like five years?
"Yeah, so I can wear my glamour nighty for two hours. And then an hour later, I’m in a meeting look tackling the job I love.
"That’s the two-fold life of a woman with chronic illness; we still rock our dreams and goals and passions (and fashions) and we live many lives in one day.
"Tell me about your day!"
This article originally appeared in The Sun.