A very common type of arthritis is way undertreated. coming up next Psoriatic arthritis undertreated Jennifer Davis writing in Arthritis Today reported on a study published in JAMA Dermatology. About half of all patients with psoriasis and psoriatic arthritis PsA are dissatisfied with the treatment they are getting, according to the new study. Moreover, the study found a large percentage of study participants are either undertreated or not getting any treatment at all. I think the numbers are significant especially for the psoriatic arthritis population, says lead author April W. Armstrong, MD, assistant clinical professor of dermatology and director.