The pigmented purpuras are a group of idiopathic rashes that can occur at any age. They are grouped together because of their similar clinical and histological presentations. They are believed to be caused not by vasculitis but by inflammation of the small cutaneous capillaries, which produces a capillaritis. The rash is typically of no clinical significance to the patient, but it can cause significant cosmetic concern, and the purpuras need to be differentiated from other conditions that can cause similar rashes. The five rashes that make up the pigmented purpuric family of rashes are Schamberg’s disease, eczematous pigmented purpura of Doucas and Kapetanakis, pigmented purpura of Gougerot and Blum, lichen aureus, and Majocchi’s disease (annular telangiectatic pigmented purpura).
Clinical Findings: These entities are grouped together for many reasons. They are believed by some to be slightly different manifestations of the same disease state, and the histopathology of all the variants is strikingly similar. The pigmented purpuric dermatoses are benign and are not associated with any underlying abnormality. They can occur at any age. They are almost entirely asymptomatic in nature. The true incidence of these conditions is unknown, because they are often not reported. They are believed to occur very commonly.
Schamberg’s disease is the most frequently encountered of the pigmented purpuric eruptions. It almost universally begins on the lower extremities. It manifests as tiny (1-mm) cayenne pepper–like petechial macules of the skin. Over time, a brownish-red hyperpigmented background forms secondary to the extravasation of red blood cells and their subsequent breakdown within the skin to release hemosiderin. The lesions are nonblanching and nonpalpable. The rash may spread proximally up the lower extremity but rarely affects other areas of the body. Most patients are referred to the dermatologist to rule out vasculitis, which is easily done by not finding any evidence of palpable purpura. The rash is almost always entirely asymptomatic, and patients frequently complain only of the appearance. If one sees widespread petechia, a platelet count should be performed to look for thrombocytopenia. If the platelet count is normal, a skin biopsy of the upper extremity or truncal area of involvement should be performed to evaluate for the very rare form of pigmented purpuric mycosis fungoides.
Eczematoid pigmented purpura of Doucas and Kapetanakis is a rare variant that manifests with petechiae and hyperpigmentation but is also associated with an overlying eczematous eruption. This form is typically pruritic and can show secondary excoriations.
Pigmented purpura of Gougerot and Blum is also known as lichenoid pigmented purpura. Small, light pink to purple papules form on the lower extremities. They can be mistaken initially for lichen planus. Biopsies of these papules show a lichenoid infiltrate. This pigmented purpura can be distinguished from Schamberg’s disease in that the skin findings are palpable. There is no true palpable purpura.
Lichen aureus can be seen at any age and manifests with the presence of multiple tiny, golden-colored macules that coalesce into a large macule or patch. Lichen aureus can occur anywhere on the body and is solitary in nature.
The involved regions in Majocchi’s disease show annular patches with petechiae and hyperpigmentation from hemosiderin deposition. This is a rare form of pigmented purpura that typically starts on the legs and spreads slowly over time.
Pathogenesis: The pigmented purpuric dermatoses are believed to be caused by capillaritis. The exact etiology is unknown.
Histology: The histological findings are similar across all variants. Extravasation of red blood cells is prominent. The extravasation is seen in the vicinity of the capillaritis. The infiltrate is predominantly lymphocytic. The presence of hemosiderin is more easily seen in chronic lesions.
Treatment: There is no agreed-upon standard therapy, and withholding therapy is a frequently used option. Anecdotally, topical corticosteroids may be tried for a few weeks. Oral vitamin C and bioflavonoids have been reported to be successful, again mostly in anecdotal reports.