Adalimumab Biosimilar-Induced Severe Paradoxical Palmoplantar Pustulosis in a Patient with Psoriasis and Psoriatic Arthritis Successfully Treated with Ixekizumab

Psoriasis vulgaris is a chronic immune-mediated inflammatory disease of the skin. Biologic therapy has been available for more than 10 years and has become one of the standard treatments for patients with moderate to severe psoriasis. Initially, only biologics against tumour necrosis factor alpha (TNF-α) were used, and only later did drugs against different interleukins (ILs), including IL-17 or IL-23, became available. The side effects of biologic therapy include paradoxical adverse events (PAEs), such as palmoplantar pustular reaction, especially with anti-TNF-α drugs. We present the case of a 49-year-old female patient with diabetes and psoriasis and psoriatic arthritis treated with an adalimumab biosimilar who developed a severe PAE of the palmoplantar pustular type. Treatment with adalimumab was stopped and the patient switched to ixekizumab which was successful. When a paradoxical reaction develops during biologic therapy, especially when it is severe as in our patient, switching to another class of biologics is advised.