Multiple Keratoacanthomas Associated with Genetic Syndromes: Narrative Review and Proposal of a Diagnostic Algorithm

Keratoacanthoma (KA) is a relatively common, fast-growing epithelial tumour, with characteristic behaviour and clinical variability. Although it appears as a solitary lesion in a majority of cases, multiple KAs do occur, secondary to skin exposure to ultraviolet radiation, chemical carcinogens or certain medications, but may also be associated with various genetic syndromes. Thus, multiple KAs may serve as an early clinical alarm sign. Prompt diagnosis of the underlying cause and identification of the mechanism of development are critical for the secondary prevention of associated organ disorders or neoplasias, the improvement of patient quality of life and familial counselling. Although research in this field has seen important progress in the last few years, there are still many pathogenic processes that have not been elucidated. Additionally, the literature on this topic is limited to individual case reports and small case series, making it difficult for clinicians to parse available data and select the essential information. Therefore, this work aims to review current knowledge, summarizing existing studies, with focus on multiple KAs associated with genetic syndromes, and proposes a diagnostic algorithm for these rare cases to help guide clinicians in their practice. Lastly, we aim to highlight the main gaps in understanding the underlying mechanisms and suggest further research avenues.