Pigmenting Purpuric Dermatoses: Striking But Not a Manifestation of COVID-19 Infection

Pigmented purpuric dermatoses (PPDs) are characterized by petechiae, dusky macules representative of postinflammatory hyperpigmentation and dermal hemosiderin, and purpura generally localized to the lower extremities. They typically represent a spectrum of lymphocytic capillaritis, variable erythrocyte extravasation from papillary dermal blood vessels, and deposition of hemosiderin, yielding the classic red to orange to golden-brown findings on gross examination. Clinical overlap exists, but variants include Schamberg disease (SD), Majocchi purpura, Gougerot-Blum purpura, eczematoid purpura of Doucas and Kapetanakis (DK), and lichen aureus.¹ Other forms are rarer, including linear, granulomatous, quadrantic, transitory, and familial variants. It remains controversial whether PPD may precede or have an association with cutaneous T-cell lymphoma.² Dermoscopy usually shows copper-red pigmentation in the background, oval red dots, linear vessels, brown globules, and follicular openings. Although these findings may be useful in PPD diagnosis, they are not applicable in differentiating among the variants.

Pigmented purpuric dermatoses can easily be mistaken for stasis dermatitis or cellulitis, as these may occur concomitantly or in populations at risk for all 3 conditions, such as women older than 50 years with recent trauma or infection in the affected area. Tissue biopsy and clinical laboratory evaluation may be required to differentiate between PPD from leukocytoclastic vasculitis or the myriad causes of retiform purpura. Importantly, clinicians also should differentiate PPD from the purpuric eruptions of the lower extremities associated with COVID-19 infection.

Pigmented Purpuric Dermatoses

Schamberg Disease—In 1901, Jay Frank Schamberg, a distinguished professor of dermatology in Philadelphia, Pennsylvania, described “a peculiar progressive pigmentary disease of the skin” in a 15-year-old adolescent boy.³ Schamberg disease is the most common PPD, characterized by pruritic spots resembling cayenne pepper (Figure 1) with orange-brown pigmented macules on the legs and feet.⁴ Although platelet dysfunction, coagulation deficiencies, or dermal atrophy may contribute to hemorrhaging that manifests as petechiae or ecchymoses, SD typically is not associated with any laboratory abnormalities, and petechial eruption is not widespread.⁵ Capillary fragility can be assessed by the tourniquet test, in which pressure is applied to the forearm with a blood pressure cuff inflated between systolic and diastolic blood pressure for 5 to 10 minutes. Upon removing the cuff, a positive test is indicated by 15 or more petechiae in an area 5 cm in diameter due to poor platelet function. A positive result may be seen in SD.⁶

FIGURE 1. Schamberg disease. Dusky, red-brown, nonscaling macules resembling cayenne pepper on the legs.

Histologically, SD is characterized by patchy parakeratosis, mild spongiosis of the stratum Malpighi, and lymphoid capillaritis (Figure 2).⁷ In addition to CD3⁺, CD4⁺, CD8⁺, CD1a⁺, and CD36⁺ lymphocytes, histology also may contain dendritic cells and cellular adhesion molecules (intercellular adhesion molecule 1, epithelial cell adhesion molecule 1) within the superficial perivascular infiltrate.⁸ There is no definitive therapy, but first-line interventions include emollients, topical steroids, and oral antihistamines. Nonpharmacologic management includes compression or support stockings, elevation of the lower extremities, and avoidance of offending medications (if identifiable).¹

FIGURE 2. Histopathology of pigmented purpuric dermatoses. Orthokeratosis and focal spongiosis overlying a superficial perivascular lymphocytic infiltrate with occasional extravasated erythrocytes (H&E, original magnification ×20).

Majocchi Purpura—Domenico Majocchi was a renowned Italian dermatologist who described an entity in 1898 that he called purpura annularis telangiectodes, now also known as Majocchi purpura.⁹ It is more common in females, young adults, and children. Majocchi purpura has rarely been reported in families with a possible autosomal-dominant inheritance.¹⁰ Typically, bluish-red annular macules with central atrophy surrounded by hyperpigmentation may be seen on the lower extremities, potentially extending to the upper extremities.¹ Treatment of Majocchi purpura remains a challenge but may respond to narrowband UVB phototherapy. Emollients and topical steroids also are used as first-line treatments. Biopsy demonstrates telangiectasia, pericapillary infiltration of mononuclear lymphocytes, and papillary dermal hemosiderin.¹¹

Gougerot-Blum Purpura—In 1925, French dermatologists Henri Gougerot and Paul Blum described a pigmented purpuric lichenoid dermatitis known as Gougerot-Blum purpura,¹² a rare PPD characterized by lichenoid papules that eventually coalesce into plaques of various colors, along with red-brown hyperpigmentation.⁴ As with other PPD variants, the legs are most involved, with rare extension to the trunk or thighs. The plaques may resemble and be mistaken for Kaposi sarcoma, cutaneous vasculitis, traumatic purpura, or mycosis fungoides. Dermoscopic examination reveals small, polygonal or round, red dots underlying brown scaly patches.¹³ Gougerot-Blum purpura is found more commonly in adult men and rarely affects children.⁴ Histologically, a lichenoid and superficial perivascular infiltrate composed of lymphocytes and macrophages is seen. Various therapies have been described, including topical steroids, antihistamines, psoralen plus UVA phototherapy, and cyclosporin A.¹⁴

Eczematoid Purpura of Doucas and Kapetanakis—In 1949, Greek dermatologists Christopher Doucas and John Kapetanakis observed several cases of purpuric dermatosis similar in form to the “pigmented purpuric lichenoid dermatitis” of Gougerot-Blum purpura¹² and to the “progressive pigmentary dermatitis” of Schamberg disease.³ After observing a gradual disappearance of the classic yellow color from hemosiderin deposition, Doucas and Kapetanakis described a new bright red eruption with lichenification.¹⁵ Eczematoid purpura of Doucas and Kapetanakis is rare and predominantly seen in middle-aged males. Hyperpigmented or dark brown macules may develop bilaterally on the legs, progressing to the thighs and upper extremities. Unlike the other types of PPD, DK is extensive and severely pruritic.⁴