survey included additional questions about managing PsA patients that may provide more insights into the potential underdiagnosis of this disease. More than one third of the surveyed US dermatologists reported that the greatest challenge in managing their PsA patients was differentiating PsA from other arthritic diseases. However, fewer than 10 % felt they would need to refer to or involve other specialists in the care of their PsA patients. The surveyed US rheumatologists reported delayed referrals as the second most common challenge in treating PsA patients. Fewer than 40 % of physicians reported co-management of PsA patients. Most often, this relationship consisted of a rheumatologist primarily being responsible for prescribing decisions and a dermatologist monitoring skin symptoms. A recent review and meta-analysis provided recommendations for dermatologists regarding screening, diagnosing, and treating PsA patients [19]. Educating dermatologists to routinely discuss and evaluate joint disease with their psoriasis patients—and providing guidance on when to refer them to a rheumatologist—may 94 M. G. Lebwohl et al. bring about more timely diagnosis and treatment of patients with PsA. Co-management and/or collaborative efforts among dermatologists and rheumatologists may ensure that psoriasis patients, while receiving care for their skin disease, are also adequately screened and further assessed for the presence of PsA. Despite expanding therapeutic options for managing psoriasis and PsA patients, undertreatment remains a challenge [9, 13]. Although approximately 70 % rated their disease as moderate or severe [15], US patients participating in the MAPP survey reported low treatment rates, with only about 10 % of psoriasis patients reporting treatment with conventional oral or biologic therapy. US dermatologists reported nearly three times greater current use of conventional oral therapies and more than seven times greater current use of biologic agents for their psoriasis patients than were reported by the surveyed US patients. Likewise, while dermatologists and rheumatologists reported systemic therapy use in the majority of PsA patients, only half of the PsA patients reported current use of oral or biologic therapy. There are several possible explanations for these discrepancies. Patients included in the MAPP survey were not required to be seeing an HCP or receiving treatment at the time of the survey, and patients and physicians were not matched. Patients may have been seeing another specialist or a primary care physician for their disease. It is possible that seeing a primary care physician rather than a physician specializing in dermatologic or rheumatic conditions contributed to the lower treatment rates reported by the patients than by the participating physicians. In addition, approximately 20 % of psoriasis patients reported having no skin lesions as reasons for not seeing an HCP, suggesting that treatment would not be required. However, although higher rates of treatment were reported by physicians than by patients, physicians indicated that more than 30 % of patients were still not receiving systemic therapy for their moderate to severe psoriasis or for PsA at the time of the survey, in contrast to guideline recommendations [20, 21]. In addition, other surveys have also shown a high level of undertreatment. In the 2011 NPF survey, up to one third of patients were not receiving treatment for their moderate or severe psoriasis, and of the patients who were receiving treatment, an estimated 20–30 % were receiving topical monotherapy [13]. The complexity and time-consuming nature of treating patients with psoriasis and PsA may contribute to undertreatment. Most dermatologists reported that managing their psoriasis patients takes up more of their time than managing other patients, and approximately one third of dermatologists and rheumatologists described the care of patients with PsA as complicated and time consuming. Comorbidities, which were reported by the majority of patients, may also be a contributing factor to the complexity of treating psoriasis and PsA patients. In addition, multiple physicians providing care to an individual patient may lead to miscommunication or confusion over roles in prescribing decisions, and may contribute to lower treatment rates, emphasizing the importance of communication among HCPs. Dissatisfaction with current therapies may impact disease management and treatment. The most commonly cited barriers to use of conventional oral therapy, across patients, dermatologists, and rheumatologists, were concerns with long-term safety and tolerability, and lack of effectiveness. Patients also reported laboratory monitoring (16.4 %) and lifestyle modification (7.0 %) as being among the top three reasons contributing