Your long standing history of discoid lupus
becomes significant here and I presume you are on some treatment for your psoriasis/arthritis with an immunosuprressive agent. The common ones (at the start) are hydroxychloroquine
, then methotrexate (weekly once), sulfasalazine
to lower the amount of steroid use.
The painful lumps could either be your discoid worsening or some form of urticarial vasculitis
that needs to be excluded.
For the timebeing, you can either increase the steroid use (if you are on steroids) or start using a long-acting antihistamine like fexofenadine 180mg twice daily until you have seen your Lupus doctor.