Acral acanthotic anomaly: a comprehensive review

Acral acanthotic anomaly (AAA), also referred to as acral acanthosis nigricans (AAN), is a variant of acanthosis nigricans characterized by hyperpigmented, hyperkeratotic plaques localized to acral surfaces, particularly the knuckles, toes, and dorsal aspects of the hands and feet. Unlike other common forms, AAA is not typically associated with obesity, insulin resistance, or endocrinopathy. Its pathogenesis remains poorly understood. The aim of this article is to provide a comprehensive synthesis of the literature on AAA, including its epidemiology, clinical features, histopathologic findings, reported cases, and associated systemic associations. A narrative review of the literature was conducted using PubMed to identify articles discussing AAA. Relevant case reports and reviews were examined to extract data on presentation, histology, differential diagnosis, and potential clinical associations. Existing literature consistently describes a characteristic acral distribution and histologic features such as papillomatosis, hyperkeratosis, and basal pigmentation. Although often observed in otherwise healthy individuals, the literature demonstrates the potential for association with malignancy or autoimmune disease. Due to the rarity of AAA, available data are limited to case reports and small series, with no large-scale studies or longitudinal follow-up. Accurate recognition of AAA is essential to guide clinical evaluation, avoid unnecessary testing, and identify potential systemic associations when present.