Capillaritis (pigmented purpuric dermatoses, purpura pigmentosa)

Management Strategy

Diagnostic hallmarks are the yellow-brown or orange patches with superimposed pinpoint cayenne pepper spots, which represent petechiae and persist with diascopy. Thus, biopsies are warranted when in doubt.

Dermoscopic examination shows a coppery-red to brownish diffuse coloration of the background, round to oval red dots, globules or patches, and gray dots (probably accumulation of hemosiderin-containing macrophages) and a partial network of interconnected pigmented lines.

The main differential diagnoses are petechiae in thrombocytopenia (<10.000–20.000/mm ³ ) and small vessel vasculitis; a discerning criterion from the latter would be a palpable infiltrate (palpable or retiform purpura) when present, but there are courses or variants of small vessel vasculitis with petechial maculae only (e.g., IgA vasculitis or recurrent macular vasculitis in hypergammaglobulinemia [hypergammaglobulinemic purpura of Waldenström]).

Thus, biopsies are warranted when in doubt. Allergic contact dermatitis (e.g., in response to textile or azo dyes) may be purpuric or hemorrhagic, but with intense pruritus. The pigmented purpuric dermatitis-like variant of mycosis fungoides also needs to be excluded. Suspicion would be raised by poikiloderma, pruritus, coalescing plaques, and a duration of more than 1 year. Exclusion of mycosis fungoides may require repeated biopsies. Linear morphea was seen to develop in the same anatomic distribution as prior lichen aureus, warranting follow-up especially in pediatric patients.

Capillaritis has a benign course and therefore must be differentiated from these more serious diseases.

Usually there is no need for treatment unless the patient has pruritus or suffers from cosmetic disfigurement.

Detection and avoidance of possible eliciting agents should always be attempted. Reported causes include:

• Drugs (14% in one series), e.g., non-steroidal antiinflammatory drugs (NSAIDs) (acetaminophen, acetylsalicylic acid), bromine-containing drugs, carbamazepine, meprobamate, chlordiazepoxide, furosemide, nitroglycerine, interferon-α, raloxifene (selective estrogen receptor modulator), thiamine (vitamin B1), sildenafil, or topical 5-fluorouracil. As a rule, drug-induced capillaritis is more generalized and does not usually present with epidermal involvement or lichenoid infiltrate; its onset is around 10 days after intake of the suspected drug.

• Dietary supplements or ingredients: reported triggers include creatine or coca cola and apple-cherry fruit spritzer, as well as ingredients of an energy drink (vitamin B complex, caffeine, taurine).

• Chronic infections such as viral hepatitis B or C (though relation is questionable) or odontogenic infections.

When the etiology remains obscure, therapy has to be empirical. Local corticosteroids, calcineurin inhibitors, or ultraviolet (UV) 311 nm ( preferred to psoralen plus UVA [PUVA]) have been tried. Increased venous pressure (particularly in the legs) or exercise are not direct causes but can aggravate capillaritis. In these cases, compression stockings may be helpful.

There is some evidence for increased vascular permeability or vascular fragility due to subtle defects in the extracellular matrix. This may explain reported responses to bioflavonoids (which may be due to inhibition of elastase and hyaluronase and of leukocyte activation), ascorbic acid ( antioxidant effects and perhaps reduction of vascular permeability), and calcium dobesilate (reduction of microvascular permeability in part by antioxidant properties).