The pigmented purpuric dermatoses (PPDs) are a rare group of chronic, benign diseases characterized by multiple petechiae on hyperpigmented, yellowish-brown macules.1 The different variants are distinct clinical forms of the same entity with similar histopathologic features.2,3

There are 5 classic variants: Schamberg disease (progressive PPD), eczematoid purpura of Doucas and Kapetanakis (pruritic purpura), pigmented purpuric lichenoid dermatosis of Gougerot and Blum, lichen aureus (lichen purpuricus), and Majocchi disease (purpura annularis telangiectodes).1 Less common variants are granulomatous PPD, itching purpura of Loewenthal, linear PPD, transitory PPD, and familial PPD.2

PPDs are rare and predominantly affect adults,1 although cases have been reported in children.4 The most common variant in both adults and children is Schamberg disease. PPDs, and linear forms in particular,6 are generally more common in men.1 Majocchi disease is more common in women.

Although the causes of the PPDs are unknown, a range of triggering factors have been proposed, including exercise, venous hypertension, diabetes mellitus, infections,2,7 and various medications (Table 1).8 An association with dyslipidemia and autoimmune diseases has been reported for granulomatous PPD.9 In most cases, however, no cause is identified.10

Capillary dilation and fragility have been attributed a possible pathogenic role in PPDs.10 It has been hypothesized that the cells responsible for these disorders are cells involved in blood vessel structure, such as fibroblasts and endothelial cells. Whether through activation (e.g., high intravascular pressure) or spontaneously, the function of these cells may be altered, causing red blood cells (RBCs) to leak through the vessel walls,11 triggering a cell-mediated hypersensitivity reaction. Cell-mediated immune response would therefore appear to have a fundamental role in the pathogenesis of PPDs.12,13 The perivascular inflammatory infiltrate is made up of CD4+ T cells14 (with reduced CD7 expression15) and CD1a+ dendritic cells.12

The pathogenic role of cell adhesion molecules in PPDs has also been analyzed in several studies. CAMs are membrane proteins that interact with specific ligands that provide and maintain contact between different cells and between cells and extracellular matrix proteins. High expression levels have been observed for adhesion molecules LFA-1 (lymphocyte function antigen-1) and ICAM-1 (intercellular adhesion molecule-1) in inflammatory cells and for ICAM-1 and ELAM-1 (endothelial leukocyte adhesion molecule- 1)12 in endothelial cells. T cells activated by an antigenic stimulus would thus adhere to endothelial cells, fibroblasts, and keratinocytes.16 Cytokines produced by leukocytes (e.g., tumor necrosis factor α) can trigger the expression of these adhesion molecules (Fig. 1).

Figure 1.

Etiologic and pathogenic mechanism. One of the most widely accepted hypotheses is that T cells are activated by an antigenic stimulus and bind to endothelial cells, fibroblasts, and keratinocytes through the expression of adhesion molecules. TNF-α indicates tumor necrosis factor α ; ICAM-1, intercellular adhesion molecule-1; LFA-1, lymphocyte function antigen-1.

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The above cytokines may also result in a decreased release of the endothelial plasminogen activator and/or an excessive increase in the plasminogen activator inhibitor,17 leading to the reduced fibrinolytic activity and intraperivascular deposition of fibrin observed in PPDs.18

Direct immunofluorescence may show fibrinogen, immunoglobulin M, and/or C3 deposition in the superficial dermal vessels.10

Another hypothesis that has emerged in recent years is that PPDs may represent an insidious epitheliotropic T-cell alteration. This theory is supported by the observation of epidermotropism or a monoclonal pattern in the inflammatory infiltrate.15,19 There have even been some reports of progression to mycosis fungoides.20–22 As it is difficult to distinguish between purpuric mycosis fungoides and monoclonal PPD, it is essential to integrate clinical, molecular, and histopathologic findings.15,20,23 Poikiloderma, pruritus, coalescing plaques, a duration of more than 1 year, a monoclonal pattern, and decreased CD7 and CD62 L expression in the infiltrate should all raise suspicion of disease progression, even in the absence of overt lymphocytic atypia.15,24 Some authors opt to treat disseminated and monoclonal DPP as early-stage mycosis fungoides.

Histopathologically, PPDs are characterized by a perivascular lymphocytic infiltrate centered on the superficial small vessels. Other typical findings are endothelial swelling, luminal narrowing,10 extravasated RBCs, and hemosiderin-laden macrophages (Fig. 5 A and B). Perls and Fontana-Masson staining shows hemosiderin (iron) deposits in the superficial dermis, setting DPP apart from stasis dermatitis, which has deeper deposits.2

Figure 5.

Histopathological features of Schamberg disease. A, Infiltrate involving small vessels in the superficial dermis. B, Lymphocytic infiltrate, with luminal narrowing and extravasated red blood cells.

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A characteristic finding of lichen aureus is an intact epidermis separated from a band-like dermal infiltrate by an area of spared connective tissue (Grenz area)27 (Fig. 6). This infiltrate is also typical in pigmented purpuric lichenoid dermatosis of Gougerot and Blum.26 Eczematoid purpura of Doucas and Kapetanakis, by contrast, features epidermal spongiosis and neutrophils in the infiltrate.25 Granulomatous PPD is characterized by a perivascular granulomatous infiltrate overlying typical features.38 A comparison of clinical features, location, and histopathologic findings for the most common variants of PPD is provided in Table 2.

Figure 6.

Histopathologic features of lichen aureus. Band-like infiltrate in the papillary dermis and superficial perivascular infiltrate.

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While some authors1,13 consider capillaritis to be a defining feature of DPPs, Ackerman40 does not believe this to be the case as there is an absence of fibrin in the luminal wall and thrombi in the lumina.

In addition to skin biopsy, a blood test is recommended to rule out thrombocytopenia, clotting or autoimmune disorders (antinuclear antibodies, rheumatoid factor), and chronic infections (anti-HCV and anti-HBsAg).2

Dermoscopy

The most common dermoscopic finding is a diffuse coppery-red background that histopathologically corresponds to the lymphocytic dermal infiltrate, extravasated RBCs, and hemosiderin-laden macrophages.41 Other findings include red globules and dots, which can be explained by the extravasated RBCs, the increased number of blood vessels, and the dilation of these vessels42 (Fig. 7). Brown dots are observed in almost 50% of patients and correspond to the spherical or elliptical arrangement of melanocytes and melanophages at the dermoepidermal junction. In a third of cases, dermoscopy shows a pigmented pseudo-network that corresponds to the hyperpigmented basal cell layer and incontinentia pigmenti in the papillary dermis. Specific dermoscopic findings reported for lichen aureus include a coppery-red background with brown and red dots and globules, gray dots, and a pseudo-network comprising interconnected pigmented lines43 (Fig. 8).

Figure 7.

Dermoscopic features of Schamberg disease. Coppery-red background and red globules.

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Figure 8.

Dermoscopic features of lichen aureus. Brownish-red background with gray dots and a pigmented pseudo-network.

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Considering that DPPs are benign and no standardized treatments with proven effectiveness exist, the risks and benefits of any treatment should be carefully weighed up.

Due to the benign, largely asymptomatic nature of the DPPs, no treatment is an option.4 Treatment, however, is often called for because of the chronic nature of the disease, its physical and psychological impacts, and the presence of extensive lesions or itching.

Most of the treatment recommendations are based on small case series, and none of them are backed by sufficient evidence to be considered a universal treatment.

A range of topical and systemic treatments, detailed below, have been described in small series and case reports.

The DPPs are a common dermatological condition and have a major impact on patient quality of life due to both symptoms and cosmetic concerns. Although the different variants are clinically very similar, there are a number of clinical, histopathologic, and dermoscopic characteristics that help to establish a more specific diagnosis.

Finally, while there is insufficient evidence in the literature to recommend any treatment as a first-line treatment, numerous options exist that can achieve considerable improvements.

The authors declare that they have no conflicts of interest.