The immunological implications of paradoxical reactions in rheumatoid arthritis and psoriasis treatment: A case report

Psoriasis and rheumatoid arthritis (RA) are common chronic diseases with distinctive histological and molecular features. However, there are similarities in their immunological pathogenesis, leading to the use of some similar systemic biological treatment. In 5% of patients using biological therapy such as the anti-tumor necrosis factor alpha (anti-TNF-α), a paradoxical reaction (i.e., the exacerbation or development of one disease while treating the other) may develop. We report a case of a 27-year-old female diagnosed with seropositive RA who developed paradoxical psoriasis (PP) after the use of Adalimumab, an anti-TNF-α, and paradoxical eczema due to the use of Ixekizumab, an anti-interleukin-17A, for the treatment of PP. This case demonstrates the occurrence of two different types of paradoxical skin reactions in a single patient. This case also highlights the importance of the selection and cessation of biological treatment in similar cases, as well as the factors that might predict the development of paradoxical reactions to promote the safe usage of biological therapy.