Background The global use of artificial intelligence has the potential to revolutionize the healthcare industry. Despite the fact that artificial intelligence is becoming more popular, there is still a lack of evidence on its use in dermatology. Objective The study aimed to determine the capacity of ChatGPT-3.5 and ChatGPT-4 to support dermatological knowledge and clinical decision-making in medical practice. Methods Three dermatology specialty certificate tests, in English and Polish, consisting of 120 single-best-answer, multiple-choice format questions each, were used to assess ChatGPT-3.5 and ChatGPT-4 performance. Results ChatGPT-4 exceeded the 60% pass rate in every performed test, with a minimum of 80% and 70% correct answers for the English and Polish versions, respectively. ChatGPT-4 performed significantly better on each exam (p<0.01), regardless of the language, compared to ChatGPT-3.5. Furthermore, ChatGPT-4 answered clinical picture-type questions with an average accuracy of 92.98% and 84.21% for English and Polish questions respectively. The difference between the tests in Polish and English did not turn out to be significant but still, ChatGPT-3.5 and ChatGPT-4 in English performed better overall than in Polish by an average of 8 percentage points for each test. Incorrect ChatGPT answers were highly correlated with a lower difficulty index, which denotes questions with higher difficulty in most of the tests. (p<0.05) Conclusion The dermatological knowledge level of ChatGPT was high, with a significantly better performance of ChatGPT-4 than ChatGPT-3.5. Although the use of ChatGPT will not replace the doctor's final decision, physicians should support artificial intelligence development in dermatology to raise the standards of medical care.

Hydroxyurea therapy is commonly used in the treatment of patients suffering from myeloproliferative diseases, such as polycythemia vera. It is supported by evidence that this type of therapy can generate mild skin lesions like leg ulcers, erythema, and hyperpigmentation. There are also some studies that show an increased risk of development of nonmelanoma skin cancers. We report a 56-year-old man with a 13-year history of polycythemia vera, treated chronically with hydroxyurea. In April 2020, the patient presented a skin lesion on the forehead, skin horn on the left forearm, and hyperkeratosis on the rims of both ears. In the patient’s history, in October 2019, complete excision of the skin lesion in the central area of the forehead was performed. After 4 months, a new skin lesion appeared at the same area of the forehead, which in May 2020 after resection in the histopathological examination was diagnosed as recurrence of squamous cell carcinoma. The aim of the case is to draw the clinicians’ attention to the increased risk of squamous cell carcinoma and basal cell carcinoma in patients treated with hydroxyurea. Increased vigilance would make it possible to recognize them earlier, and thus potentially reduce the undesirable effects associated with the delayed radical treatment of these skin cancers. Randomized clinical trials assessing the potential benefits of oral retinoids for chemoprevention of nonmelanoma skin cancers in the hydroxyurea-treated population should also be considered.