First the ones you probably did not know were about Rare Disease:
“Detective Pikachu” 2019 – The mastermind of the plot (Bill Nighy) has a rare degenerative disorder and is in a wheelchair. He seeks a cure by genetically engineering lab rats... er I mean Pokemon. This results in a new serum called "Serum R". What does the R stand for? They never say. Could it stand for Rare?
“Glass” 2019 – Mr. Glass has Type I osteogenesis imperfecta. Director M. Night Shyamalan has two parents and a wife who are doctors so he probably gets his disease details right. Read more here.
“The Favorite” 2018— Queen Anne (Olivia Colman) most likely suffered from Antiphospholipid syndrome (APS), also called Hughes syndrome. Anne's symptoms create the opening for Sarah Marlborough (Rachel Weisz) and later Abigail (Emma Stone) to ingratiate herself as a care giver, massaging and tending her legs. Read more here.
“The Greatest Showman” 2018 – Those circus “freaks”? Historically many of them had rare diseases. Based on a true story. Read more here.
“Arrival” 2016 – Amy Adams plays a rare disease mom, it's backstory but it alters her world view, which alters the plot. Read more here.
“The Big Sick” 2016 – A meet cute comedy about a girlfriend in a coma due to the rare disease adult-onset Still's disease (AOSD). Based on the true story of Emily V. Gordon and Kumail Nanjiani (Silicon Valley).
”Danny Collins” 2015 — Al Pacino plays an aging rock-star who decides to change his life and find the adult son he’s never met. The son (Bobby Cannavale) turns out to be battling a rare form of leukemia. Very loosely based on a true story.
Next the ones you probably already knew were about Rare Disease:
“Five Feet Apart” 2019 – Cystic Fibrosis keeps teen lovers apart. Six feet apart is the required safe distance to avoid infection. The film's treatment of this became controversial in the CF community. Read more here.
“Midnight Sun” 2018 – The disease, XP, literally makes Katie (Bella Thorne) a star-crossed lover. Read more here.
“Extraordinary Measures” 2010 – John Crowley starts his own research lab to save his kids from Pompe disease. Based on a true story.
"Lorenzo's Oil" 1992 – The Odone family’s search for a treatment for adrenoleukodystrophy (ALD). Based on a true story.
"The Elephant Man" 1980 – Directed by David Lynch. Based on a true story. Joseph Merrick likely had Proteus syndrome or neurofibromatosis.