Version May 2024
INTRODUCTION — Purpura are nonblanchable, hemorrhagic skin lesions that result from the leakage of red blood cells into the skin. The term "retiform purpura" describes lesions that demonstrate an angulated or branched configuration (picture 1A-C). Retiform purpura can occur in a variety of disorders; thus, identifying the underlying cause is an important component of patient management.
The potential causes of retiform purpura and the approach to the assessment of patients with these lesions will be reviewed here. Additional details on the pathogenesis, clinical manifestations, and treatment of disorders that present with retiform purpura are discussed elsewhere in UpToDate. (See 'Associated disorders' below.)
Cutaneous vasculitis, a potential cause of purpura (including retiform purpura), is reviewed in greater detail separately. The differential diagnosis of purpura in children is also reviewed separately. (See "Overview of cutaneous small vessel vasculitis" and "Evaluation of adults with cutaneous lesions of vasculitis" and "Purpuric skin lesions (petechiae, purpura, and ecchymoses) in children: Evaluation".)
CLINICAL FINDINGS — Retiform purpura are nonblanchable, persistent, dark red to dark purple, hemorrhagic patches or plaques that occur on the skin and exhibit a characteristic branched configuration (picture 1A). Lesions may be relatively small (eg, 1 to 2 cm) or more than 10 cm in diameter and may be limited to a focal area of skin, particular body region, or widespread (picture 1B, 1D-E). Widespread retiform purpura, termed "purpura fulminans," can represent a life-threatening condition. (See 'Recognition of life-threatening emergencies' below.)
Prominent, peripheral erythema may occur in lesions that develop secondary to inflammatory processes and areas of necrosis due to tissue infarction may be present (picture 2). Pain within lesions is common and may be severe.
PATHOPHYSIOLOGY — Retiform purpura develop as a consequence of complete vascular occlusion and vascular damage involving blood vessels in the skin. Lesions may occur in the setting of intravascular abnormalities in which thrombi, proteins, or emboli obstruct cutaneous vessels, or may involve direct damage to vessel walls, as occurs in vasculitis, calciphylaxis, and some severe opportunistic infections.
As in livedo reticularis (picture 3A-B) and livedo racemosa (picture 4) (additional disorders associated with vasculopathy or vasculitis), the angulated or branched shape of retiform purpura reflects the vascular architecture in the skin (see 'Differential diagnosis' below). The hemorrhagic appearance of purpura results from the local extravasation of red blood cells. Skin necrosis results from infarction.
ASSOCIATED DISORDERS — Multiple vasculopathic disorders may present with retiform purpura [1].
Intravascular abnormalities — Thrombosis, intravascular deposition of abnormal proteins, and embolic phenomena may result in the development of retiform purpura.
Thrombotic and coagulopathic disorders
●Disseminated intravascular coagulation (DIC) – DIC may occur in the setting of sepsis, organ failure, trauma, malignancy, and other severe disorders, such as homozygous protein C deficiency in neonates. Patients with DIC exhibit clinical manifestations of both hemorrhage and thrombosis. Purpura may be widespread (purpura fulminans), and the disorder can be fatal (picture 1B, 1F) [2,3]. Meningococcemia is a common cause of DIC. (See 'Recognition of life-threatening emergencies' below and "Evaluation and management of disseminated intravascular coagulation (DIC) in adults" and "Disseminated intravascular coagulation in infants and children".)
●Hypercoagulable states – Hypercoagulable states, such as antiphospholipid syndrome, may lead to retiform purpura. The mechanisms through which antiphospholipid antibodies in serum lead to thrombosis are not completely understood (picture 1C-D). Common additional features of antiphospholipid syndrome include livedo reticularis, livedo racemosa, cutaneous infarctions or ulceration, recurrent venous or arterial thromboses, and fetal loss [4-7]. Examples of other hypercoagulable states that may present with retiform purpura include antithrombin III deficiency, protein C/S deficiency, prothrombin III mutation, factor V Leiden, and hyperhomocysteinemia [1]. (See "Clinical manifestations of antiphospholipid syndrome" and "Diagnosis of antiphospholipid syndrome".)
●Thrombotic thrombocytopenic purpura (TTP) – TTP is a rare, idiopathic disorder characterized by microangiopathic hemolytic anemia, thrombocytopenia, neurologic abnormalities, and renal disease [8,9]. Nonretiform purpura related to thrombocytopenia are often present. (See "Diagnosis of immune TTP".)
●Warfarin-induced skin necrosis – This condition results from the development of a transient, hypercoagulable state secondary to warfarin-induced reduction of protein C (an anticoagulant) early in the course of warfarin therapy. Purpura are extensive and demonstrate a predilection for areas with significant adipose tissue (eg, thighs, buttocks, abdomen, breasts (picture 5A-C)). Patients with underlying protein C deficiency are at increased risk for this disorder [10-12]. (See "Protein C deficiency", section on 'Warfarin-induced skin necrosis'.)
●Heparin-induced thrombocytopenia – Heparin-induced thrombocytopenia is an immune-mediated disorder that usually occurs 5 to 10 days after treatment with heparin [13,14]. Necrotic, purpuric lesions may occur at sites of subcutaneous heparin injection or in areas distant from the site of administration (heparin necrosis). Patients may also exhibit large vessel venous or arterial thromboses [13,14] (see "Management of heparin-induced thrombocytopenia"). Heparin necrosis may also occur in the absence of thrombocytopenia (picture 6A-B).
●Paroxysmal nocturnal hemoglobinuria – This rare disorder due to a defect in the PIG-A gene is characterized by venous thrombosis and hemolysis, resulting in hemoglobinuria. In addition to retiform purpura, patients may present with bullae, petechiae, or ulcerations. (See "Clinical manifestations and diagnosis of paroxysmal nocturnal hemoglobinuria" and "Treatment and prognosis of paroxysmal nocturnal hemoglobinuria".)
Intravascular protein deposition
●Cryoglobulinemia (type I) – In type 1 cryoglobulinemia, retiform purpura develop in the setting of blood hyperviscosity and blood vessel occlusion due to the precipitation of immunoglobulins in response to cold. Lesions are often found on acral areas; livedo reticularis, acrocyanosis, and infarction may also be present (picture 7) [15,16]. (See "Overview of cryoglobulins and cryoglobulinemia".)
●Cryofibrinogenemia – Cryofibrinogenemia results from the precipitation of fibrin, fibrinogen, and/or fibronectin in plasma during cold exposure. Like cryoglobulinemia, retiform purpura are often acral. Additional findings may include livedo reticularis, livedo racemosa, and painful ulcerations [17]. (See "Disorders of fibrinogen", section on 'Cryofibrinogenemia'.)
●Paraproteinemia – Rarely, paraproteinemia induces blood hyperviscosity and plugging of vessels, resulting in the development of retiform purpura [18].
Embolic disorders — Embolic disorders that may lead to retiform purpura include cholesterol emboli, septic emboli, atrial myxoma, and other disorders:
●Cholesterol emboli – Retiform purpura associated with cholesterol embolization are often located on the distal lower extremities (picture 8A-B). Other cutaneous features include livedo reticularis, livedo racemosa, gangrene, cutaneous infarction, ulceration, and cyanosis (blue toe syndrome) (picture 9). Renal, gastrointestinal, ocular, or central nervous system abnormalities may also occur. Many patients exhibit eosinophilia [19,20]. (See "Embolism from atherosclerotic plaque: Atheroembolism (cholesterol crystal embolism)".)
●Septic emboli – Purpura due to septic emboli most commonly occur in the setting of infectious endocarditis but may also occur in other forms of septicemia. Lesions are typically acral. Other cutaneous findings, such as petechiae or Janeway lesions, may be present. (See "Clinical manifestations and evaluation of adults with suspected left-sided native valve endocarditis".)
●Atrial myxoma – Atrial myxomas are benign tumors of the heart. Tumor fragments may embolize systemically, and patients often exhibit constitutional symptoms (eg, fever, weight loss) [21,22]. As with other embolic phenomena, lesions are often acral. (See "Cardiac tumors", section on 'Myxomas'.)
●Other – Emboli resulting in vessel occlusion and retiform purpura may also occur in nonbacterial thrombotic endocarditis (marantic endocarditis, Libman-Sacks endocarditis) and hypereosinophilic syndrome. (See "Nonbacterial thrombotic endocarditis" and "Hypereosinophilic syndromes: Clinical manifestations, pathophysiology, and diagnosis".)
Vessel wall pathology — Damage to vessel walls resulting in retiform purpura may occur in vasculitis, various opportunistic infections, calciphylaxis, and primary hyperoxaluria:
●Vasculitis – Vasculitis is defined by the presence of an inflammatory infiltrate invading blood vessel walls and fibrinoid necrosis (fibrin deposition within vessel walls or lumina). Retiform purpura are classically seen in vasculitides that affect medium-sized cutaneous vessels. In contrast, small vessel vasculitis most often presents with nonretiform palpable purpura. (See "Evaluation of adults with cutaneous lesions of vasculitis", section on 'Diagnostic criteria' and "Evaluation of adults with cutaneous lesions of vasculitis".)
Examples of vasculitides that may present with retiform purpura include:
•Septic vasculitis – Vasculitis presenting with retiform purpura may occur in meningococcemia, gonococcemia, pseudomonal or streptococcal septicemia, rickettsial infections, infective endocarditis, and other infectious states [23-25]. In the setting of severe infection, retiform purpura may also result from DIC. (See "Clinical manifestations of meningococcal infection" and 'Recognition of life-threatening emergencies' below.)
•Vasculitis related to autoimmune disease or primary systemic vasculitis (eg, rheumatoid arthritis, systemic lupus erythematosus, cutaneous or systemic polyarteritis nodosa, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis [Churg-Strauss]). (See "Evaluation of adults with cutaneous lesions of vasculitis".)
•Cryoglobulinemic vasculitis (cryoglobulinemia types 2 and 3) [15,26]. (See "Overview of cryoglobulins and cryoglobulinemia" and "Mixed cryoglobulinemia syndrome: Clinical manifestations and diagnosis".)
●Opportunistic infections – In immunocompromised patients, invasion of infectious organisms into blood vessel walls and lumina may result in vessel occlusion and the development of retiform purpura. This phenomenon may be seen in association with pseudomonal infection (ecthyma gangrenosum (picture 10)), invasive fungal infections (eg, mucormycosis, aspergillosis, candidiasis), disseminated strongyloidiasis, and in lepromatous leprosy as a feature of the Lucio phenomenon.
•(See "Pseudomonas aeruginosa skin and soft tissue infections", section on 'Ecthyma Gangrenosum'.)
•(See "Mucormycosis (zygomycosis)".)
•(See "Epidemiology and clinical manifestations of invasive aspergillosis".)
•(See "Strongyloidiasis".)
●Calciphylaxis – Calciphylaxis is a life-threatening disorder characterized by the deposition of calcium in blood vessels (picture 2). This condition almost always occurs in the setting of advanced, chronic renal failure. Extremely painful retiform purpura may develop; lesions frequently occur in adipose-rich areas, such as the buttocks, abdomen, or thighs. Other cutaneous features include livedo reticularis, livedo racemosa, and cutaneous infarction [27,28]. (See "Calciphylaxis (calcific uremic arteriolopathy)".)
●Primary hyperoxaluria – Primary hyperoxaluria is a rare, autosomal recessive, metabolic disorder that results in the overproduction of oxalate. Patients develop renal stones and calcium oxalate deposits in multiple tissues, including blood vessels [29,30]. The cutaneous lesions of primary hyperoxaluria are similar to calciphylaxis. (See "Primary hyperoxaluria".)
Other — Examples of other conditions that may present with retiform purpura include livedoid vasculopathy, pyoderma gangrenosum, and vasculopathy or vasculitis due to levamisole-contaminated cocaine:
●Livedoid vasculopathy – Livedoid vasculopathy (also known as atrophie blanche) is a cutaneous disease characterized by the development of fibrin thrombi in cutaneous vessels. The condition typically manifests as recurrent, small, purpuric, ulcerative lesions on the distal lower extremities (picture 11). Pale scars with stippled telangiectasia are left after healing [31-33]. (See "Livedoid vasculopathy".)
●Pyoderma gangrenosum – Pyoderma gangrenosum is an inflammatory skin disorder that typically presents with ulceration. Infrequently, it may present with retiform purpura that evolve into ulcers that exhibit the violaceous edges classically seen in this disorder. Pyoderma gangrenosum may occur in association with inflammatory bowel disease, inflammatory arthritis, or hematologic malignancies [34-36]. (See "Pyoderma gangrenosum: Pathogenesis, clinical features, and diagnosis".)
●Thrombotic vasculopathy or vasculitis due to levamisole-contaminated cocaine – Use of cocaine contaminated with levamisole has been associated with the development of tender purpura on the ears and necrotic, retiform purpura on the trunk or extremities (picture 12A-C). (See "Cocaine: Acute intoxication", section on 'Levamisole'.)
DIFFERENTIAL DIAGNOSIS — Retiform purpura must be distinguished from nonpurpuric skin disorders that may exhibit a branched configuration, such as livedo reticularis and livedo racemosa, as well as other types of purpuric lesions.
Livedo reticularis and livedo racemosa are nonpurpuric disorders that present with accentuated vascular patterns in the skin. Livedo reticularis, which results from the slowing of blood flow through cutaneous vessels, presents as a blanchable, reticulated vascular pattern with a red-blue or violaceous hue (picture 3A-B). Livedo racemosa, which develops in the setting of irregular impairment of blood flow, is characterized by a more abrupt, patchy, and broken vascular pattern with or without areas of necrosis (picture 4). In some conditions, retiform purpura may coexist with livedo reticularis or livedo racemosa. (See 'Associated disorders' above and "Evaluation of adults with cutaneous lesions of vasculitis", section on 'When to suspect cutaneous vasculitis'.)
The configuration of retiform purpura distinguishes these lesions from petechiae and purpura due to trauma or bleeding diatheses. Such lesions typically lack the angulated shape of retiform purpura (picture 13A-B).
PATIENT ASSESSMENT — The assessment of patients with retiform purpura focuses on early recognition of patients with acute, life-threatening disease that requires immediate intervention and the detection of the underlying cause of purpura formation [1]. In general, the evaluation should include at least a patient history, physical examination, skin biopsy, and select laboratory tests. The need for additional microbiologic and radiologic testing is based upon the clinical presentation.
Recognition of life-threatening emergencies — Examples of acute and immediately life-threatening conditions that may present with retiform purpura include disseminated intravascular coagulation (DIC; a disorder that may occur due to sepsis, trauma, malignancy, obstetric emergencies, neonatal homozygous C deficiency, or other causes) and opportunistic infections. Mortality from these conditions can be high, and prompt evaluation is necessary for these patients.
Findings that should prompt investigation for these disorders include:
●Purpura fulminans (acute development of widespread retiform purpura (picture 1A, 1E, 1G))
●Signs or symptoms of sepsis and/or shock
●Other signs of severe illness (fever, organ failure, altered mental status)
●Acute development of retiform purpura in an immunocompromised patient
Immediate initial tests for such patients should include [1]:
●Complete blood count with differential
●Comprehensive metabolic panel
●Urgent skin biopsy (see 'Skin biopsy' below)
●Erythrocyte sedimentation rate and/or C-reactive protein level
●Urine toxicology
In addition, the presence of purpura fulminans should prompt:
●Laboratory evaluation for DIC (see "Evaluation and management of disseminated intravascular coagulation (DIC) in adults", section on 'Diagnostic evaluation' and "Disseminated intravascular coagulation in infants and children", section on 'Diagnosis')
There should be a high suspicion for infection in patients with purpura fulminans or with signs of sepsis and in immunocompromised patients with retiform purpura. The initial evaluation of these patients should include:
●Lesional punch biopsy for tissue culture (see 'Assessment for infection' below)
●Evaluation for sepsis (cultures [blood and other suspected sites of infection], blood tests, and radiologic imaging, as indicated) and consideration of broad-spectrum antibiotic and antifungal coverage while awaiting results
•(See "Evaluation and management of suspected sepsis and septic shock in adults".)
•(See "Sepsis in children: Definitions, epidemiology, clinical manifestations, and diagnosis".)
●Tests for specific suspected infections (eg, invasive aspergillosis)
Patient history — The medical history should be obtained with particular emphasis on factors that may assist with the identification of the underlying disorder, such as:
●Symptoms of infection
●History of thrombotic disease, which may suggest antiphospholipid syndrome or genetic disorders characterized by hypercoagulability:
•Deep venous thromboses or pulmonary emboli
•Recurrent, spontaneous abortions
•Family history of thrombotic events
●Drug history, which may suggest warfarin-induced skin necrosis, heparin-induced thrombocytopenia, or vasculopathy or vasculitis due to levamisole-contaminated cocaine
●History of organ dysfunction:
•Renal failure, which may suggest calciphylaxis
•History of heart murmur or valve dysfunction, which may suggest endocarditis or atrial myxoma
●History of myeloproliferative conditions and blood dyscrasias, which may suggest occlusion related to blood hyperviscosity
●History of hyperlipidemia, ischemic heart disease, or peripheral vascular disease, which may suggest atheroemboli
●History of or symptoms of connective tissue disease or primary systemic vasculitis, which may suggest vasculitis related to rheumatoid arthritis, systemic lupus erythematosus, polyarteritis nodosa, granulomatosis with polyangiitis, or eosinophilic granulomatosis with polyangiitis (EGPA; Churg-Strauss)
●Exacerbation of lesions with cold exposure, which may suggest cryoglobulinemia or cryofibrinogenemia
Physical examination — A full physical examination and skin examination should be performed. The examination confirms that the cutaneous findings are consistent with retiform purpura and allows for the detection of features suggestive of an underlying cause. In particular, the skin examination should assess the appearance, palpability, and distribution of purpuric lesions, as well as the presence of other cutaneous findings.
Lesion color and palpability — Retiform purpura are typically dark red to dark purple, and unlike erythema associated with nonpurpuric, inflammatory skin disorders, the color of purpura fails to blanch under pressure. Diascopy (application of pressure to a lesion with a glass slide) can be used to confirm the nonblanchable nature of a purpuric lesion.
In some cases, early lesions demonstrate significant erythema, which suggests the presence of a primary inflammatory process [37]. These inflammatory lesions are frequently palpable and may appear in the following conditions:
●Vasculitis
●Livedoid vasculopathy
●Pyoderma gangrenosum
Retiform purpura associated with noninflammatory, intravascular, occlusive vasculopathies may be palpable or macular but typically lack prominent erythema. (See 'Intravascular abnormalities' above.)
Areas of necrosis due to tissue infarction may occur in both noninflammatory and inflammatory lesions.
With time and the breakdown of extravasated hemoglobin, purpura may develop a greenish or yellow-brown color.
Lesion distribution — The clinical distribution of lesions may assist in diagnosis (table 1). As examples:
●Retiform purpura in areas with significant adipose tissue, such as the buttocks, thighs, and abdomen, may occur in warfarin-induced skin necrosis or calciphylaxis.
●Retiform purpura predominantly involving lower extremities may occur in vasculitis, livedoid vasculopathy, cholesterol emboli, or calciphylaxis.
●Retiform purpura primarily involving acral areas may occur in septic vasculitis, embolic disorders, cryoglobulinemia, or cryofibrinogenemia.
●Widespread, extensive purpura (purpura fulminans) may occur in infection, DIC, or warfarin-induced skin necrosis.
●The presence of unilateral lesions may suggest embolic phenomena.
Associated physical findings — The presence of additional cutaneous or extracutaneous findings should be assessed. As examples, the detection of a heart murmur, splinter hemorrhages (picture 14), Osler nodes (picture 15), or Janeway lesions (picture 16) suggests infectious endocarditis, and respiratory symptoms may occur in patients with EGPA or granulomatosis with polyangiitis (table 2).
The detection of additional cutaneous findings may also assist with diagnosis. As an example, livedo reticularis (picture 3A-B) is a common feature of several disorders that may present with retiform purpura, such as antiphospholipid antibody syndrome, polyarteritis nodosa, cholesterol emboli, and cryoglobulinemia.
Skin biopsy — Skin biopsies offer insight into the pathogenic mechanism of retiform purpura and, therefore, can be useful for diagnosis. We advocate the performance of skin biopsies in most patients.
Type and location of biopsy — Evaluation of vessels in the dermis and subcutis is important in retiform purpura. Thus, punch or incisional wedge biopsies are performed, rather than more superficial shave biopsies. (See "Skin biopsy techniques".)
Preferred sites for biopsies for histopathologic examination include areas that are painful or tender; biopsying both from the center and the edge of a lesion may also increase the diagnostic yield [38]. Areas of frank necrosis or ulceration should be avoided, since necrotic tissue may fail to demonstrate diagnostic histopathologic findings. In addition, biopsies of necrotic areas may demonstrate an inflammatory response resembling primary vasculitis in patients with nonvasculitic disorders [37].
The approach to biopsies for tissue culture for patients with findings suggestive of infection differs. (See 'Assessment for infection' below.)
Vasculitis is a common cause of inflammatory retiform purpura. The approach to the biopsy of lesions that are suspicious for vasculitis is reviewed separately. (See "Evaluation of adults with cutaneous lesions of vasculitis", section on 'Skin biopsy to confirm vasculitis'.)
Assessment of biopsy results — Several histopathologic patterns are associated with retiform purpura; a table correlating histopathologic findings with specific disorders is provided (table 3).
Assessment for infection — When infection is suspected, a tissue specimen should also be sent for culture. A punch biopsy from the center of a retiform purpura lesion that shows early signs of necrosis is ideal [1].
Other techniques that may be helpful for assessing for infection include aspiration and culture of fluid within hemorrhagic bullae, scraping of the roof of bullae for potassium hydroxide preparations, and smearing of tissue specimens on a glass slide for a touch preparations [1]. (See "Office-based dermatologic diagnostic procedures", section on 'Potassium hydroxide preparation'.)
Laboratory tests — Routine initial laboratory studies for the stable patient with noninflammatory retiform purpura include [37] (see 'Intravascular abnormalities' above):
●Complete blood count with platelets and differential
●Blood smear
●Partial thromboplastin time
●Hepatic and renal function tests
●Cryoglobulins in patients with lesions and symptoms suggestive of this disorder (eg, acral lesions exacerbated by cold exposure) (see "Overview of cryoglobulins and cryoglobulinemia", section on 'Detection of cryoglobulins')
●Antineutrophil cytoplasmic antibodies
The diagnostic utility of these laboratory studies is described in a table (table 4). Additional tests may be ordered based upon the results of these studies, skin biopsy findings, and suspicion of the underlying disorder. In cases in which infection is suspected, blood and/or urine cultures should be obtained.
Patients with noninflammatory, nonvasculitic retiform purpura in whom a thrombotic disorder is suspected (eg, with a personal history or strong family history of venous thromboembolism and/or other findings suggestive of these disorders) may benefit from testing for antiphospholipid syndrome and inheritable thrombophilias. (See "Evaluating adult patients with established venous thromboembolism for acquired and inherited risk factors", section on 'Patient selection for additional testing' and "Evaluating adult patients with established venous thromboembolism for acquired and inherited risk factors", section on 'Hypercoagulable tests' and "Thrombophilia testing in children and adolescents", section on 'Approach to thrombophilia testing'.)
Patients with inflammatory retiform purpura should be evaluated for the possibility of vasculitis. (See 'Lesion color and palpability' above and "Evaluation of adults with cutaneous lesions of vasculitis".)
Patients with purpura fulminans require assessment for DIC. (See 'Recognition of life-threatening emergencies' above and "Evaluation and management of disseminated intravascular coagulation (DIC) in adults", section on 'Diagnostic evaluation' and "Disseminated intravascular coagulation in infants and children", section on 'Diagnosis'.)
MANAGEMENT — The treatment of retiform purpura is dependent upon correction of the underlying etiology. (See 'Associated disorders' above.)
SUMMARY AND RECOMMENDATIONS
●Clinical findings – Retiform purpura are hemorrhagic skin lesions characterized by an angulated or branched appearance (picture 1A-C). The shape of retiform purpura is reflective of the pattern of the underlying vascular network. (See 'Clinical findings' above and 'Pathophysiology' above.)
●Pathophysiology – Retiform purpura occur as a consequence of disrupted vascular flow in the skin or subcutis. Disorders that cause vessel occlusion through thrombosis, intravascular protein deposition, emboli, or vessel wall destruction are associated with the development of these lesions (table 2). (See 'Pathophysiology' above.)
●Life-threatening presentations – The acute appearance of extensive purpura, termed "purpura fulminans," is a life-threatening disorder that occurs in the setting of disseminated intravascular coagulation (DIC). Identification of the underlying cause of DIC is essential for management. Retiform purpura may also occur in the setting of life-threatening, opportunistic infections. Prompt evaluation of patients with purpura fulminans, with signs of sepsis or severe illness, or in immunocompromised states is essential. (See 'Recognition of life-threatening emergencies' above.)
●Patient assessment:
•History and physical examination – A thorough history and physical examination may provide valuable clues for diagnosis and should be performed in all patients who present with retiform purpura. The skin examination should include assessment of the color and distribution of purpura (table 1). (See 'Patient assessment' above.)
•Skin biopsy – Skin biopsies of retiform purpura can provide useful diagnostic information (table 3). We perform a skin biopsy in almost all patients. A punch or excisional wedge biopsy should be performed to allow for adequate evaluation of vessels in the dermis and subcutis. Areas of necrosis should be avoided. A tissue culture should be performed if infection is suspected. (See 'Skin biopsy' above.)
•Laboratory tests – An appropriate initial laboratory workup for stable patients with noninflammatory retiform purpura includes a complete blood count with differential and platelets, blood smear, partial thromboplastin time, hepatic and renal function tests, cryoglobulins in patients with acral lesions exacerbated by cold exposure, and antineutrophil cytoplasmic antibodies (table 4).
Additional tests may be added based upon these results, skin biopsy findings, and the likelihood of specific disorders. If infection is suspected, blood, tissue, and/or tissue cultures should be performed. (See 'Laboratory tests' above.)
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