8.7 Purpuric rashes

Purpura. Purpuric skin eruptions.

Variable prevalence depending on the etiology.

Purpura is not a specific nosologic or diagnostic term, but includes a heterogeneous group of benign, purpuric skin eruptions characterized by red to purple macules, patches and petechiae secondary to capillary leakage of different mostly unknown causes. 

Purpura is often a symptom indicative of an underlying cause of bleeding (see classification). 

Purpuric rashes may be primary (when hemorrhage is an integral part of lesion formation) or secondary (hemorrhage takes place in previously established lesions).

Increase fragility and permeability of vessels in elderly people, venous hypertension or drugs (glucocorticosteroids, anticoagulants) may be promoting factors.

According to the aetiology, different purpuric rashes could be defined:

1. Purpuric rashes secondary to coagulation disorders (thrombocytopenic).

2. Purpuric eruptions secondary to vascular damage (vasculitis) or vascular damage with thrombosis.

3. Purpuric eruptions secondary to vascular occlusion (hypercoagulable states, emboli, medium-large sized vasculitis).

4. Miscellaneous. Secondary to vascular fragility, perivascular inflammation, drug induced purpura, pressure.

Purpuric non-palpable, non-blanchable, red-brown to golden-brown (due to erythrocyte extravasation and hemosiderin deposition) lesions can be divided according their size in: 

• Petechiae (capillary, punctiform hemorrhages with a limit of up to 4mm).

• Macular purpura (sized up to a centimeter).

• Macular ecchymoses, (larger amount of extravasation of erythrocytes).

Occasionally confluent, or associated with edematous plaques, blisters, or pustules.  Can be accompanied by gingival, conjunctival or gastrointestinal (GI) bleeding, hematuria, or by internal hemorrhage according to the etiology.

In some disorders, fever and a toxic syndrome may be present. Tenderness may suggest an inflammatory process.

Purpuric rashes could be localized or generalized with a variable localization. May be present in acral areas, or in dependent areas often on the lower extremities.

Depending on the association of a febrile illness or constitutional/toxic/drug-induced/food additives and food colouring symptoms.

Purpuric rashes can be classified as:

1. Non-palpable and afebrile rash.

• eczematid-like purpura: pruritic scaly petechial plaques.
• lichen aureus: localized yellow-brown patches.
• purpura annularis telangiectodes: annular macules.
• Schamberg disease: multiple patches with pinpoint petechiae on the lower limbs.
• coagulation disorders.
• idiopathic thrombocytopenic purpura.
• hemorrhagic pigmentary dermatoses (Gougerot-Blum, Majocchi).
• Scurvy (follicle bound).
• Genodermatoses (i.e. Ehlers-Danlos syndrome).
• physical/mechanic by pressure (vomiting, strangulation, coughing).

2. Non-palpable and febrile rash.

• Infectious coagulopathies.

• Virus (i.e. Ebola).

• Meningococci (i.e. purpura fulminans).

3. Palpable and afebrile rash. Small vessel vasculitis.

• Leukocytoclastic vasculitis.

• ANCA-related vasculitis.

4. Palpable or non-palpable and febrile.

• Infectious disorders. Potentially life-threatening conditions. Vasculitis Meningococcemia, bacterial endocarditis, rickettsiosis, disseminated  gonococcal infection,  systemic vasculitis,  purpuric viral exanthems.

5. Retiform and afebrile: Embolic conditions. Hypercoagulable states, late stages of Nicolau  syndrome; anticoagulant induced necrosis; calciphylaxis, vasculopathies; anticardiolipin syndrome.

6. Retiform and febrile: Septic vasculitis, thrombosis,  purpura fulminans, disseminated  intravascular coagulation.

7. Senile purpura: Severe dematoporosis with stasis.

Glass spatula and Rumpel-Leede test. Complete hematological survey. Platelet count and coagulation tests. Biochemistry (liver and renal functional tests, plasma electrophoresis); immunological serum tests, stool guaiac (fecal occult blood test), urinalysis may be performed according the suspected underlying diagnoses. Specific microbiological cultures: in cases of suspected of an underlying infectious disease.

The hallmark of purpuric lesions is extravasation of erythrocytes around the capillaris and venules and interstitial with or without vasculitis signs. Mixed pattern of purpura and eczema.

Depending on the underlying etiology. Acute, subacute, chronic.

Depending on the underlying etiology from self-limited to lethal outcome.

Clinical evaluation: All ages: Some purpuric rashes are almost exclusively observed in children (Henoch-Schönlein purpura) or in elder patients (senile purpura).

Clinical history. Acute or prolonged evolution of lesions. Possible precipitating events (contacts with infectious persons or agents, drugs). 

Physical examination: Skin and mucous membranes. Rash distribution and progression. Skin biopsy in cases of palpable purpuric rash or febrile purpuric eruptions.

Associated systemic symptoms (fever, hypotension).

Exclude secondary hemorrhagic variants of common diseases (hemorrhagic disseminated zoster, cellulitis etc.). Exclude minor conditions with hemorrhagic lesion (senile purpura, skin areas treated with topical corticosteroids, petechial facial purpura due to vomiting or coughing).

Depending on the underlying etiology.

None.