8.7 Purpuric rashes

Cutaneous skin eruption with purpuric lesions.

Purpura is defined as visible hemorrhage (extravasated erythrocytes) into the skin or mucous membranes. Purpura is not a specific nosologic or diagnostic term, but includes a heterogeneous group of benign, skin eruptions characterized by red to purple macules, patches, and petechiae due to secondary capillary leakage. A broad spectrum of causes including blood clotting, thrombopenia, thrombocyte dysfunction, infections, reactive or autoimmune processes, etc. may give rise to purpuric rashes.

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). Increased fragility and permeability of vessels in elderly people or due to treatment (glucocorticosteroids, anticoagulants, drugs, hematological diseases, etc.) may be promoting factors.

According the etiology different purpuric rashes could be defined:

1. Purpuric rashes secondary to coagulation abnormalities (thrombocytopenic)

   Genetic and acquired disorders: Impaired platelet production and function, genetic abnormalities in coagulation factors, excessive platelet consumption such as disseminated intravascular coagulation, immune thrombocytopenia, drug-induced thrombocytopenia, etc.

2. Purpuric eruptions secondary to vascular damage (vasculitis) Clinically manifested as purpuric palpable lesions (palpable purpura):

   • Leukocytoclastic vasculitis (small-vessels): Perivascular inflammation, vascular damage and erythrocyte extravasation. Multiple etiologies.

   • Leukocytoclastic vasculitis + thrombosis: Severe infections (septicaemia, meningococcal infections, measles),

3. Purpuric eruption secondary to vascular occlusion

   • Clinically manifested as cutaneous purpuric lesions with a retiform (net-like) pattern. May be inflammatory and non-inflammatory.

   • Different etiologies: Hypercoagulable states, emboli, medium-large sized vasculitis

4. Miscellanea. Secondary to vascular fragility, perivascular inflammation, etc.

5. Congenital diseases: Connective tissue diseases (Ehlers-Danlos syndrome), congenital infectious disorders (TORCH): cytomegalovirus (CMV), rubella. Drug-induced purpura, age-related (senile) purpura, secondary to trauma, factitial, etc.

Purpura is clinically manifested as non-blanchable red-brown to golden-brown (due to erythrocyte extravasation and hemosiderin deposition) lesions in which the application of external pressure does not leads to disappearance of the red colour.

Purpuric non-palpable lesions can be divided according their size in:

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

• Macular purpura (sized up to a centimetre).

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

In purpuric rashes skin eruption may be manifested by lesions of variable size, extension and distribution. Occasionally confluent, or associated with edematous plaques, blisters, or pustules. Can be accompanied by gingival 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.

Depending on the association of a febrile illness or constitutional/toxic symptoms.

Purpuric rashes can be classified as:

1. Non-palpable and afebrile rash

   Frequently associated with:

   • Coagulation disorders

     • Platelet-related disorders, thrombocytopenic purpura (idiopathic or secondary). Coagulation factor deficiencies.

   • Entities presenting erythrocyte extravasation secondary to perivascular inflammatory infiltrates (without vasculitis)

     • Pigmented purpuric eruptions: Group of disorders manifested as petechiae and pigmentary macules. Include:

       • Progressive pigmented purpura (Schamberg disease): Multiple patches with pinpoint petechiae on the lower limbs

       • Purpura annularis telangiectodes (Majocchi): Annular plaques

       • Pigmented purpuric lichenoid dermatosis (Gougerot-Blum): Lichenoid purpuric papules/plaques

       • Eczematide-like purpura: Pruritic scaly petechial plaques

   • Lichen aureus: Localized, persistent, purpuric golden-brown macules.

   • Diseases associated with non-inflammatory vessel wall dysfunction or fragility:

     • Scurvy, genetic conditions (Ehlers-Danlos, Marfan’s syndrome etc.), senile purpura (severe dematoporosis with stasis), amyloidosis and Cushing’s disease, physical/mechanic by pressure (vomiting, strangulation, coughing)

2. Non-palpable and febrile rash

   • Infectious coagulopathies:

     • Tropical viral hemorrhagic fevers (dengue, yellow fever, Ebola)

     • Cocci (Purpura fulminans)

3. Palpable and afebrile rash.

   • Leukocytoclastic vasculitis

     • Cutaneous small-vessels vasculitis, including IgA vasculitis (Henoch-Schönlein purpura), cryoglobulinemic vasculitis, urticarial vasculitis, ANCA-related vasculitis (microscopic polyangiitis, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis [Churg-Strauss disease]

4. Palpable and febrile.

   • Infectious disorders. Potentially life-threatening conditions.

     • Meningococcemia, bacterial endocarditis, rickettsiosis, disseminated gonococcal infection, purpuric viral exanthems.

   • Non-infectious: Systemic vasculitis, ANCA-related vasculitis.

5. Retiform and afebrile.

   • Embolic conditions. Hypercoagulable states.

     • Nicolau syndrome; anticoagulant induced necrosis; calciphylaxis, vasculopathies; anticardiolipin syndrome.

6. Retiform and febrile.

   • Vasculitis + thrombosis.

     • Septic vasculitis, post-infectious purpura fulminans, HELLP syndrome.

Thrombotic thrombocytopenic purpura.

The hallmark of purpuric lesions is extravasation of erythrocytes around the capillaries and venules and interstitial with or without vasculitis signs. Skin biopsy in cases of palpable purpuric rash or febrile purpuric eruptions.

• Clinical evaluation: Age: 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 (sick contacts, drugs)

• Physical examination: Skin and mucous membranes. Rash distribution (symmetrical or asymmetrical) and progression.

• Associated general bruising or systemic symptoms (fever, hypotension). In selected cases hepatomegaly/splenomegaly or neurological signs.