INTRODUCTION
Palmoplantar pustulosis (PPP), also known as palmoplantar pustular psoriasis, is a chronic skin disorder in which pruritic pustular eruptions appear on the palms and soles. It is thought to be a variant of psoriasis.1 Despite its localized involvement, PPP is chronic and has been shown to reduce quality of life. The disorder affects all ages, with females more likely to be affected than males.2
Although its exact cause is unknown, PPP is thought to be multifactorial and caused by a combination of genetic and environmental factors. Although the PSORS1 locus that is associated with psoriasis vulgaris is not associated with PPP, variations of IL-19, IL-20, and IL-24 genes may be associated with both psoriasis and PPP. Human leukocyte antigen (HLA) Cw6, CARD14, and ATG16L1 genes have also been associated with the conditions. Additionally, environmental triggers, such as smoking, stress, drugs, infection, sweating, repetitive trauma, and irritants play a role in the pathophysiology.3 The underlying immunologic mechanism is hypothesized to involve inflammation that destroys the acrosyringium, the primary site of sterile pustule formation. Mast cells, lymphocytes, neutrophils, and eosinophils contribute to this process. Furthermore, chemotactic factors such as IL-8 and IL-17 related cytokines, tumor necrosis factor alpha, interferon-gamma, and complement pathway activation are also thought to be involved. Genetic factors and environmental triggers spur an immune cascade, leading to immune cell proliferation and the formation of lesions on the skin.4
PPP lesions often induce itching, pain, and breakdown of the skin barrier that can be exacerbated in flares of disease. On examination, the skin contains thick, hyperkeratotic plaques and/or sterile pustules that can be symmetric, erythematous, and scaly. Although most patients only exhibit lesions on the palms and soles, nail changes, including pitting and ridging, can be observed in approximately 60% of cases. More extensive nail changes are found in Acrodermatitis continua of Hallopeau, a relatively rare subset of pustular psoriasis that classically affects the nail apparatus, giving rise to its clinical description as "nails floating away on a lake of pus." This condition can coexist with PPP and is important to recognize because it can lead to anonychia or osteolysis of the distal phalanges if left untreated. A subset of patients with PPP may also have arthritic symptoms. Associated disorders include pustulotic arthro-osteitis (PAO) and Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis syndrome (SAPHO).5 The presentation of PPP may mimic numerous other conditions such as dyshidrotic eczema, contact dermatitis, pityriasis rubra pilaris, and tinea pedis and manuum. As a result, a thorough history and physical examination are warranted, though additional workup is also
Although its exact cause is unknown, PPP is thought to be multifactorial and caused by a combination of genetic and environmental factors. Although the PSORS1 locus that is associated with psoriasis vulgaris is not associated with PPP, variations of IL-19, IL-20, and IL-24 genes may be associated with both psoriasis and PPP. Human leukocyte antigen (HLA) Cw6, CARD14, and ATG16L1 genes have also been associated with the conditions. Additionally, environmental triggers, such as smoking, stress, drugs, infection, sweating, repetitive trauma, and irritants play a role in the pathophysiology.3 The underlying immunologic mechanism is hypothesized to involve inflammation that destroys the acrosyringium, the primary site of sterile pustule formation. Mast cells, lymphocytes, neutrophils, and eosinophils contribute to this process. Furthermore, chemotactic factors such as IL-8 and IL-17 related cytokines, tumor necrosis factor alpha, interferon-gamma, and complement pathway activation are also thought to be involved. Genetic factors and environmental triggers spur an immune cascade, leading to immune cell proliferation and the formation of lesions on the skin.4
PPP lesions often induce itching, pain, and breakdown of the skin barrier that can be exacerbated in flares of disease. On examination, the skin contains thick, hyperkeratotic plaques and/or sterile pustules that can be symmetric, erythematous, and scaly. Although most patients only exhibit lesions on the palms and soles, nail changes, including pitting and ridging, can be observed in approximately 60% of cases. More extensive nail changes are found in Acrodermatitis continua of Hallopeau, a relatively rare subset of pustular psoriasis that classically affects the nail apparatus, giving rise to its clinical description as "nails floating away on a lake of pus." This condition can coexist with PPP and is important to recognize because it can lead to anonychia or osteolysis of the distal phalanges if left untreated. A subset of patients with PPP may also have arthritic symptoms. Associated disorders include pustulotic arthro-osteitis (PAO) and Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis syndrome (SAPHO).5 The presentation of PPP may mimic numerous other conditions such as dyshidrotic eczema, contact dermatitis, pityriasis rubra pilaris, and tinea pedis and manuum. As a result, a thorough history and physical examination are warranted, though additional workup is also
