Purpura, the clinical manifestation of red blood
cell extravasation into mucosa or skin, results from various conditions,
including rheumatologic, infectious, dermatologic, traumatic, and
hematologic disorders. This chapter does not address purpura resulting
from quantitative or functional deficiencies of platelets or coagulation
factors; these causes are discussed in other chapters. The differential
diagnosis of the disparate causes of nonthrombocytopenic purpura
is best approached by stratifying purpura into three types of lesions:
(1) palpable or retiform and noninflammatory, such as hyperglobulinemic
purpura of Waldenström; (2) palpable or nonpalpable but
inflammatory, such as Henoch-Schönlein purpura; and (3)
nonpalpable and noninflammatory, such as senile purpura. By accounting
for palpability, presence of inflammation, size, and shape, the
differential diagnosis of a particular lesion can be significantly
Acronyms and Abbreviations
Acronyms and abbreviations that
appear in this chapter include: ANCA, antineutrophil cytoplasmic
antibody; APS, antiphospholipid syndrome; CREST, calcinosis, Raynaud
phenomenon, esophageal motor dysfunction, sclerodactyly, and telangiectasia;
CSS, Churg-Strauss syndrome; DIC, disseminated intravascular coagulation;
HCV, hepatitis C virus; HP, hypergammaglobulinemic purpura; HSP,
Henoch-Schönlein purpura; MELAS, mitochondrial encephalopathy,
lactic acidosis, stroke-like; SLE, systemic lupus erythematosus;
WG, Wegener granulomatosis.
Purpura, from the Latin for purple, refers to visible hemorrhage
into mucous membranes or skin, which corresponds to extravasation
of red blood cells around dermal small vessels and chronic hemosiderin
deposition.1 Purpuric lesions, by definition, do
not blanch completely upon compression, as opposed to erythema.
Blanching is commonly tested by compression of skin lesions with
a glass slide, referred to as diascopy (Fig. 123–1).
Certain conditions give rise to lesions that mimic purpura with
incomplete blanching upon diascopy, but are not purpura because
no hemorrhage has occurred. Examples include disorders that impede
on the red cell flow, such as tortuous veins.1
A. Spider telangiectasia. B. Blanching
of spider telangiectasia. Note that spider telangiectasia blanches
Assessing lesion palpability is the first step in evaluating
purpuric lesions (Fig. 123–2). The
causes for palpability are varied and include fibrin deposition,
localized edema, significant cellular infiltration, and subcutaneous
extravasation of red blood cells.
Bedside approach to purpuric lesion diagnosis.
Inspecting the lesion for inflammatory changes is the next step
in evaluating purpuric lesions. The presence of pain, erythema,
and palpation for warmth and localized swelling are signs of inflammation
and suggest a vasculitis or immune complex disorder.
The shape of a purpuric lesion, either round or retiform (branching),
is important in assessing the lesion. In the absence of accompanying
inflammation, retiform purpuric lesions suggest small vessel occlusion. A
retiform, inflammatory purpuric lesion supports the diagnosis of
vasculitis as a result of immunoglobulin (Ig) complex formation....