From the Guidelines
The Auspitz sign is a clinical manifestation of psoriasis characterized by neovascularization, hyperkeratosis, and parakeratosis, resulting from an interplay of chemical signals and inflammatory processes, as described in the joint AAD-NPF guidelines of care for the management and treatment of psoriasis 1. The Auspitz sign involves several key mechanisms:
- Neovascularization: the formation of new blood vessels in the dermis, leading to increased blood flow and redness
- Hyperkeratosis: the excessive production of keratin, resulting in thickening of the stratum corneum
- Parakeratosis: the abnormal retention of nuclei in keratinocytes as they move up through the epidermis These changes contribute to the characteristic morphology of psoriasis, including the development of scaly plaques and the presence of systemic disease associations, such as arthritis and cardiometabolic diseases 1. To observe the Auspitz sign, one can gently scrape a psoriatic plaque with a glass slide or fingernail, removing silvery scales until a thin, transparent membrane is visible, and then continue gentle scraping to reveal pinpoint bleeding. The understanding of these mechanisms is crucial for developing targeted treatments for psoriasis, focusing on reducing inflammation, normalizing keratinocyte proliferation, and modulating angiogenesis, as outlined in the joint AAD-NPF guidelines of care for the management and treatment of psoriasis 1. Key factors contributing to the Auspitz sign include:
- Keratinocyte hyperproliferation, driven by chemical signals and inflammatory processes
- Rampant inflammation, underlying systemic disease associations
- The formation of elongated dermal papillae with thin overlying epidermis and dilated blood vessels, which are easily damaged, causing characteristic bleeding points.
From the Research
Mechanism of Action of the Auspitz Sign
The Auspitz sign is a clinical feature of psoriasis, characterized by the appearance of bleeding points after scales are scraped off from a psoriatic plaque. The mechanism of action of the Auspitz sign involves several histopathological changes, including:
- Neovascularization: an increase in blood vessels in the dermis, which leads to an increased blood supply to the affected area 2
- Hyperkeratosis: an increase in the thickness of the stratum corneum, the outermost layer of the epidermis, due to an abnormal maturation process of keratinocytes 3, 4
- Parakeratosis: the presence of nucleated keratinocytes in the stratum corneum, which is a characteristic feature of psoriasis 3, 4
Histopathological Changes
The histopathological changes in psoriasis are complex and involve an interplay of immune cells, cytokines, and keratinocytes. The changes include:
- Acanthosis: an increase in the thickness of the epidermal ridges 4
- Tortuous and dilated blood vessels: an increase in blood vessels in the dermis, which leads to an increased blood supply to the affected area 4
- Perivascular leukocytic infiltrate: an infiltration of immune cells, such as T cells and dendritic cells, into the dermis 5
- Munro microabscess and spongiform pustule of Kogoj: characteristic histopathological features of psoriasis, which are formed by the accumulation of neutrophils in the epidermis 4
Pathogenesis of Psoriasis
The pathogenesis of psoriasis is complex and involves a combination of genetic, epigenetic, and environmental influences. The interplay of immune cells and cytokines, including Th1/Th2 homeostasis, the Th17/Treg balance, and the IL-23/Th17 axis, plays a critical role in the development of psoriasis 5. Understanding the pathogenesis of psoriasis is essential for the development of targeted treatments that can block relevant inflammatory signaling pathways and molecules.