dear Stella Marie,
hello! i do not believe i have ever wrote to you before; but i've a nursing background along with microbiology and infectious disease. a while back i had a young man with Reiter's Syndrome. his history started with a UTI and urethritis and also conjunctivitis. he got it from a bacteria which was sexually transmitted (it's usually chlamydial or gonnorheal) and he did get a reactive arthritis in the hands and knees.
since you mentioned your friend had it after diarhhae....he or she might have gotten some fecal bacteria that got into the urinary system or some other way.
all infections wether it be bacterial like Lyme's, syphilis, chlamydia, staph or strep if left untreated will develope into an arthritis.
normally, if whatever triggered this Reiter's was contratcted from an outside source the course of treatment is great using tetracycline antibiotics and perhaps a few other antibiotics. the quicker the better so make sure your buddy is seeing a doctor.
things like this are weird! if we have a sore or something and get violent diarrhea WE MAKE OURSELVES SICKER SOMETIMES!!!!
so yea, i love bugs! so i like talking about this type of stuff. the young man i treated did well....but you have to keep track on how you are feeling. be vigile of achy joints and muscles and flu-like feelings. some bloodworks might be repeated a few times.
it's amazing how many organisms LIVE on our skin!!!! stuff that i had no idea!!! when i was in school i was like "yuck! e-coli and chlamydia are natural stuff we carry?" and fungus and all that gross stuff!!!!!!!!!!!!!!!!!!!!!
let me know how it goes. wishing the best. i'm curious on how this turns out. please keep me posted on what happens okay? i hope this was of some help...if i think of anymore cases i remember i'll post them. i'm good friends with a microbiologist if you need any specific advise or thoughts.
sincerely,
erin