Symmetrical Acral Keratoderma and Ichthyosis Vulgaris: Related or Independent?

Objective: Symmetrical acral keratoderma (SAK) is a rare dermatosis that primarily affects young males and manifests as symmetric, brownish, well-demarcated hyperkeratotic plaques on acral sites, particularly the wrists, dorsal hands, and fingers. Ichthyosis vulgaris (IV), the most common subtype of ichthyosis, is characterized by dry, rough skin with fine, adherent, diamond-shaped or polygonal scales on the extensor surfaces of the limbs and trunk. Clinical evidence frequently links the onset of SAK with the presence of IV. However, systematic analyses of this association remain limited. Materials and Methods: We searched PubMed, Web of Science, and the China National Knowledge Infrastructure (CNKI) for English- and Chinese-language literature. Results: The comparative analysis revealed key parallels and distinctions. SAK predominantly affects young males and is exacerbated in hot and humid climates. IV typically manifests in infancy or early childhood, persists lifelong, and worsens during cold, dry winters. Both disorders involve FLG mutations at distinct loci. Clinically, SAK presents as symmetrically distributed, well-demarcated tan-to-dark brown macules or papules on acral sites, excluding the palms and soles. IV is characterized by light-to-dark brown diamond-shaped or polygonal scales with central adhesion and peripheral detachment, primarily on the extensor surfaces of the lower limbs. Histopathologically, SAK shows marked hyperkeratosis, thinning of the granular layer, and increased basal melanocytes. IV demonstrates mild-to-moderate hyperkeratosis with attenuation or absence of the granular layer and follicular keratin plugs. Both conditions are managed symptomatically with topical emollients and salicylic acid. Systemic approaches differ: retinoids are frequently used for IV but are seldom indicated for SAK. Conclusion: This systematic comparative analysis delineates the salient features of SAK and IV, suggesting that they may be classified as distinct disease entities.