Localization of Treatment-resistant Areas in Patients With Psoriasis on Biologics

K.F. Hjuler; L. Iversen; M.K. Rasmussen; K. Kofoed; L. Skov; C. Zachariae


The British Journal of Dermatology. 2019;181(2):332-337. 

In This Article


This study shows the distribution of recalcitrant psoriasis among relatively well-treated patients administered biologic agents in a real-world clinical setting. Furthermore, we show the association between DLQI levels and body locations of recalcitrant psoriasis in patients with low absolute PASI scores on biologic treatment.

During the last 10–15 years, studies have been published regarding biologic treatment of so-called 'difficult-to-treat areas' such as palmoplantar, nail, scalp and intertriginous or genital psoriasis.[4,5] These areas are defined as difficult to treat because they are hard to treat with topicals, particularly the scalp and nails. However, this does not mean that they do not respond to effective systemic treatment. In this study, we assessed residual psoriasis in a group of relatively well-treated patients and found mainly recalcitrant psoriasis located at the typical localizations for psoriasis. This is illustrated by the fact that among the typical difficult-to-treat areas only the scalp showed some resistance to treatment with 19·2% of patients still having psoriasis in this location. The difficulty of treating the classical difficult-to-treat areas could be due to unrealistic expectations from patients, stigmatization, time-consuming treatment options, restricted availability for some treatments for certain areas, or reminiscence from the time when psoriasis was mainly treated with topical treatments.

Another way to look at our data is to see which areas are easy to treat with biologics. This can be done by comparing the distribution of psoriasis in our population with the distribution of psoriasis in general. In the publication by Farber and Nall from 1974 where they collected data from 5600 patients, the distribution of psoriasis showed that 54% had elements on the scalp, 55% on elbows, 41% on knees, 28% on face, 60% on trunk, 52% on upper extremities and 65% on lower extremities.[7] If this is compared with our study population it is seen that, for example, 0% of patients had residual psoriasis on the face, and the trunk was affected in 30·1%. Therefore, these particular areas can be considered easy to treat. However, firm conclusions are limited by the fact that we do not have information on the pretreatment body distribution of psoriasis in our patient population.

Another question that we have tried to answer with our study is whether psoriasis in certain body areas contributes to an impaired quality of life more than others when low absolute PASI levels are achieved, as has been previously suggested with psoriasis affecting vulnerable areas such as the scalp, face, intertriginous areas, genitals, hands, feet and nails.[8] Using the current scoring systems, in particular PASI, to capture the severity of psoriasis and area does not answer this question, as PASI does not specifically assess these skin areas. Furthermore, the PASI does not include nail psoriasis. If certain areas could affect the quality of life more than other areas, we would expect an uneven distribution between the three groups of DLQI 0–1, 2–5 and > 5 in our material. Such a difference was not observed. Furthermore, after adjustment for multiple comparisons there was no association between residual disease in specific areas and DLQI. However, the small number of patients in the group of patients with DLQI > 5 limits the external validity of the results in the subgroup of patients with low absolute PASI and moderately elevated DLQI. Generally, it has been expected that recalcitrant psoriasis in certain areas caused a larger impairment of quality of life than other areas; our data do not support this perception. The results of this study may advance the knowledge of recalcitrant psoriasis in the era of biologic agents. A better understanding of treatment-resistant body sites and how these affect quality of life is essential to guide the physicians better in an effort to optimize psoriasis treatment.

The study does have some strengths and limitations. The study is small, only well-treated patients are included and we do not have information on the pretreatment distribution of psoriasis. This limits our availability to investigate whether psoriasis in certain body sites is more or less refractory to treatment than psoriasis in other areas. Future larger studies with an in-depth characterization of pretreatment psoriasis localizations are warranted. Our findings are strengthened by using a uniform, detailed, data collection method in which the body area was divided into 26 regions. Furthermore, only experienced PASI assessors in specialized psoriasis university clinics included patients in the study.

In conclusion, in real-world clinical practice, the most common sites of recalcitrant psoriasis in patients treated with biologic agents are the anterior and posterior part of the lower leg, elbows and, to a certain extent, the scalp. The regions traditionally accepted as difficult-to-treat areas were rarely affected with recalcitrant lesions; however, the results from the scalp were often not clear. Recalcitrant psoriasis in no specific area caused greater impact on quality of life than any other area.