We present a case of a 48-year-old man with an approximately 30-year history of spiny projections on the palms, which were histopathologically consistent with spiny keratoderma. Spiny keratoderma is a rare entity of unknown etiology that has been described with both hereditary and acquired variants. The hereditary form, which is most likely the diagnosis in our patient, manifests at a younger age and is benign. The acquired variant, which presents in older adults, has been associated with a variety of systemic diseases and malignant conditions. In patients suspected of having acquired spiny keratoderma, an evaluation for malignant conditions may be warranted.

Psoriasis is present in all racial groups, but in varying frequencies and severity. Considering that small plaque psoriasis is specific to the Asian population and severe psoriasis is more predominant in the Western population, we defined Asian small and intermediate plaque psoriasis as psoriasis subtypes and compared their molecular signatures with the classic subtype of Western large plaque psoriasis. Two different characteristics of psoriatic spreading-vertical growth and radial expansion-were contrasted between subtypes, and genomic data were correlated to histologic and clinical measurements. Compared with Western large plaque psoriasis, Asian small plaque psoriasis revealed limited psoriasis spreading, but IL-17A and IL-17-regulated proinflammatory cytokines were highly expressed. Paradoxically, IL-17A and IL-17-regulated proinflammatory cytokines were lower in Western large plaque psoriasis, whereas T cells and dendritic cells in total psoriatic skin area were exponentially increased. Negative immune regulators, such as CD69 and FAS, were decreased in both Western large plaque psoriasis and psoriasis with accompanying arthritis or obesity, and their expression was correlated with psoriasis severity index. Based on the disease subtype comparisons, we propose that dysregulation of T-cell expansion enabled by downregulation of immune negative regulators is the main mechanism for development of large plaque psoriasis subtypes.