Mucocutaneous manifestations as early indicators of systemic disease: a narrative review.

Background: Mucocutaneous findings may provide important early clues to systemic disease. Because the skin, oral mucosa, eyes, and other visible mucosal surfaces are readily accessible during clinical examination, their careful assessment can contribute to earlier recognition of autoimmune, infectious, metabolic, endocrine, inflammatory, and malignant conditions. Objective: This narrative review aims to summarize clinically relevant mucocutaneous manifestations that may act as early indicators of systemic disease, with emphasis on their diagnostic significance and practical relevance for clinicians across specialties. Methods: A narrative literature review was conducted using PubMed/MEDLINE, Scopus, Web of Science, Google Scholar, and reference list screening. Literature was selected to provide a clinically balanced overview of mucocutaneous findings associated with systemic disease, including autoimmune disorders, infectious diseases, metabolic and endocrine disorders, inflammatory conditions, and paraneoplastic syndromes. Priority was given to peer-reviewed clinical studies, reviews, consensus-based sources, and dermatology references that clarified diagnostic relevance, disease associations, or clinical implications. Results: Mucocutaneous manifestations were identified across several systemic disease categories. In autoimmune disease, findings such as malar rash, photosensitivity, oral ulcers, heliotrope rash, and Gottron papules may support the diagnosis of systemic lupus erythematosus and dermatomyositis. Infectious diseases such as HIV infection and syphilis may present with oral candidiasis, oral hairy leukoplakia, mucous patches, or palmoplantar rash. Metabolic and endocrine disorders may be associated with acanthosis nigricans, eruptive xanthomas, xanthelasma, and other cutaneous markers of insulin resistance, dyslipidemia, or endocrine dysfunction. Paraneoplastic dermatoses, including necrolytic migratory erythema, malignant acanthosis nigricans, dermatomyositis, and acquired ichthyosis, may precede the diagnosis of internal malignancy. Conclusion: Recognition of mucocutaneous manifestations can support earlier diagnosis of systemic disease and guide appropriate investigation. A structured clinical approach to visible dermatologic and mucosal signs may improve diagnostic accuracy, reduce delays, and promote interdisciplinary collaboration between dermatology, internal medicine, oral medicine, ophthalmology, and primary care.