Off Sick with Psoriasis

Hi I’m new to this group! I am currently having a problem with my employer due to being off sick within the past 6 months with severe plaque and ethyromic psoriasis. My dermatologist put me on cyclosporine for 4 months then stopped it and put me on methotrexate 5 weeks ago which resulted in me being off sick again. What I basically wanting to know that is Psoriasis an autoimmune disorder and should I not be covered under the Equality Act 2010? Has anyone else had problems at work due to this?