Psoriasis vulgaris is a chronic skin disease with a high impact on quality of life, often requiring long-term systemic therapy. Although there are reliable guidelines on how to use biologic therapy and conventional systemic drugs, there are still concerns regarding exceptional cases such as those with oncological comorbidities. According to European guidelines, in case of a recent diagnosis of cancer, it is recommended to consult an oncologist (Nast et al., 2015). However, if a patient has malignant melanoma, the oncology specialist usually is a dermatologist.We present a case of a 62-year-old male patient who was diagnosed with superficial malignant melanoma with a Breslow index of 0.87 mm in 2005. The patient had previous treatment with UVB phototherapy and acitretin which was not tolerated well. However 15 mg of methotrexate led to relatively good results lasting 3 years after which the therapy lost its efficacy. Due to this setback and the fact that the patient had severe psoriasis and he was 3 years after surgery for melanoma, cyclosporine was initiated. The patient was treated for 1.5 years with cyclosporine 3 mg/kg having partial effect. In 2010 when the patient was 5 years after excision of melanoma, biologic treatment with etanercept was started. However, the patient presented with primary failure to etanercept and after 4 months he was switched to 90 mg of ustekinumab due to his weight which was over 100 kg ( Figure 1). After another 4 months his PASI score decreased from 21.6 to 2.8 ( Figure 2). The patient has now been treated for seven consecutive years with ustekinumab with no relapse of melanoma. Every 3 months, the patient has a complete physical examination and his LDH concentrations remain within normal reference ranges. No radiologic examinations were performed due to a Breslow index less than 1 mm.

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-a) 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-a 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.