Minor trauma to the skin may precipitate purpura, particularly when a patient is taking drugs such as aspirin, clopidogrel (Plavix), NSAIDs, and warfarin (Coumadin), all of which increase clotting time.
Long-term application of potent topical steroids on the skin of elderly patients may lead to ecchymoses.
Blood dyscrasias and coagulopathies, such as thrombocytopenia, leukemia, and disseminated intravascular coagulopathy can also result in petechiae and purpura.
Actinic purpura (formerly known as senile purpura) is a prevalent finding on the dorsal forearms in elderly people that are believed to result from minor trauma to an area of chronic sun exposure. Age-related thinning of skin and “fragile capillaries” are considered the cause (Fig. 27.12).
Chronic venous insufficiency of the lower extremities can result in purpura.
Benign Pigmented Purpuras
The benign pigmented purpuras (BPPs) are nonpalpable purpuras that result from capillaritis, an inflammation of the superficial dermal capillaries that leads to leakage of blood (extravasation) creating petechiae.
As their name implies, BPPs are not associated with any systemic disease.
Patients with BPP often present to medical attention for cosmetic concerns or to be reassured that the purpura is not a sign of a serious disease.
Lesions begin as nonblanching, red, pinpoint-sized macules (petechiae) or bruises (ecchymoses) that may coalesce.
Lesions are generally asymptomatic, but they may be mildly pruritic.
Older lesions become purple, then brown as hemosiderin forms.
Schamberg Purpura
It is the most common of the BPPs and occurs primarily in adults, especially in the elderly.
Characterized by the so-called “cayenne pepper” purpura (Figs. 27.13 and 27.14).
Majocchi Purpura (Purpura Annularis Telangiectodes of Majocchi)
Majocchi purpura is typically seen in adolescents and young adults on the trunk and proximal lower extremities but it may appear at any site.
Lesions consist of 1 to 3 cm annular purpura and pigmentation, often with a central clearing. The purple, yellow, or brown areas consist of telangiectasias and hemosiderin deposition (Fig. 27.15). Punctate petechiae may be seen in the borders.
Basics
The presence of palpable purpura (PP) represents a small vessel vasculitis of the skin. Cutaneous small vessel vasculitis is the result of inflammation of the blood vessels in the middle or upper dermis.
Vasculitis can be limited to the skin or involve the skin plus other organs. The most common extracutaneous sites of involvement are the gastrointestinal tract, kidneys, central nervous system, and joints.
Cutaneous vasculitis may be acute or chronic and the prognosis is good when no internal involvement is present.
Pathogenesis
Vasculitis results from the deposition of circulating immune complexes in the postcapillary venules which leads to inflammation and destruction of the blood vessel wall, a feature that is common to all forms of vasculitis.
In the skin, blood vessel destruction, accumulation of inflammatory cells, and the leakage of blood from the vessels result in the palpability of lesions. In other organ systems, similar damage to blood vessels can present with gastrointestinal bleeding, hematuria, or arthralgias.
Leukocytoclastic vasculitis is the characteristic histopathologic finding of palpable purpura and cutaneous vasculitis. Biopsy of lesions shows characteristic neutrophilic “nuclear dust.”
In the majority of cases, the cause of the cutaneous vasculitis is unknown, or idiopathic; and it may occur in the absence of any underlying systemic disease.
Less often it may be associated with a hypersensitivity to antigens from drugs (most often antibiotics, NSAIDs, allopurinol, thiazide diuretics, or hydantoins), malignancies, infectious diseases (such as beta-hemolytic streptococcal infection, viral hepatitis, particularly hepatitis C, and human immunodeficiency virus infection), cryoglobulinemias, and other underlying diseases such as systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis, and inflammatory bowel diseases.
Clinical Manifestations
Lesions present as variably sized (1 mm to 3 cm) palpable purpuric or erythematous papules, urticarial lesions or vesicles.
Lesions tend to appear in crops; are red to violaceous to purple in color and do not blanch (Fig. 27.16).
The lesions are characteristically symmetric in distribution mostly noted in dependent areas such as the lower legs and ankles and on the buttocks in bedridden patients, but any area of the skin can be involved.
Lesions may be asymptomatic, mildly pruritic, slightly painful, or very painful when ulcerated.
Infrequently, hemorrhagic vesicles or bullae may occur and develop into painful ulcerations (Fig. 27.17).
Healing takes place within 1 to 2 weeks and may result in postinflammatory hyperpigmentation and/or scarring.
Systemic symptoms occur in 5 to 20% of cases. In systemic vasculitis, symptoms are referable to the organ involved.
PP may recur; however, the majority of patients have only a single episode.
Diagnosis
Laboratory investigations that are useful for identifying any underlying disease include complete blood count, a blood chemistry panel, erythrocyte sedimentation rate, urinalysis, and stool examination for occult blood. Further studies (e.g., serum complement, antinuclear antibodies) should be directed by the patient's symptoms.
Other testing may include serum protein electrophoresis, cryoglobulins, and hepatitis C antibody for patients who have no identifiable disease.
Biopsy of fresh lesions shows characteristic leukocytoclastic vasculitis (“nuclear dust”). A biopsy performed too early or too late in its evolution may not reveal these findings.
Henoch-Schönlein Purpura (see Chapter 10: Cutaneous Manifestations of Systemic Disease)
Septic Vasculitis
Other Vasculitides
Atrophie Blanche (Livedoid Vasculopathy)
|
Differential Diagnosis 
Management 
Helpful Hint 
Points to Remember