DISCUSSION
Schamberg disease is typical of a whole class of conditions in which red blood cells (RBCs) are extravasated from slightly damaged capillaries. This results in nonblanchable purpura and subsequent hemosiderin staining caused by phagocytosis of the RBCs by macrophages. Clinically, this family of diseases present as cayenne pepper–colored macules, most of which are annular in configuration.
Schamberg is, by far, the most common of these conditions. This presentation was typical: manifestation on the knees and ankles followed by upward spread (hence the condition’s other name, progressive pigmentary purpura). Usually resolving on their own within months, these lesions are almost always asymptomatic—but nonetheless alarming to the patient.
Other equally benign, self-limited forms of capillaritis include those in which lesions are pruritic (eg, purpura of Doucas and Kapetanakis) or lichenoid (purpura of Gougerot-Blum). Another example is lichen aureus, in which only one or two lesions, more gold than brown, appear on the legs of younger patients.
There are many theories as to these conditions’ cause, the most common of which is increased intravascular pressure secondary to dependence. However, if this were so, we’d likely see a great deal more cases, since many patients have problems related to venous insufficiency.
In some cases, skin biopsy (usually 4-mm punch) is necessary to rule out more serious diseases, such as an early form of cutaneous T-cell lymphoma. When a coagulopathy is suspected, blood work is necessary to confirm or rule out the diagnosis. In this case, there was no reason to suspect coagulopathy (or scurvy), since no other signs were seen.
This patient was educated about his diagnosis and provided Web-based resources he could consult. Various treatments—topical steroids, increased vitamin C intake, and increased exposure to UV light—have been tried but with disappointing results.