I am posting this for a friend.

I am a 47 year-old caucasian woman suffering from monthly (with
my period) recurrences of Erythema Nodosum.  I get a variety of
symptoms, together or singly: raised tender red welts on legs, aching
joints, malaise (loss of stamina, headaches, sleepiness, flu-type
aches), yeast infections, and skin infections on my back only.

Testing for all the normal causes has come up with no clues.  I've had
negative test results for: TB, strep, pharyngitis, sarcoidosis, coccidio-
domycosis, mycobacterial infections, systemic infections, syphilis,
Lyme disease, and HIV.

Does anybody have any experience with this?  Ideas?  Clues?  
Suggestions?  Or, is there a doctor or clinic anywhere in the U.S. and
Canada (or anywhere for that matter) that specializes in this?  So far
I haven't been able to find one.