Anti-platelet autoantibodies in a pregnant woman with ITP will attack the patient's own platelets and will also cross the placenta and react against fetal platelets. Therefore, ITP is a significant cause of fetal and neonatal immune thrombocytopenia. Approximately 10% of newborns affected by ITP will have platelet counts <50,000/uL and 1% to 2% will have a risk of intracerebral hemorrhage comparable to infants with neonatal alloimmune thrombocytopenia (NAIT).

No lab test can reliably predict if neonatal thrombocytopenia will occur. The risk of neonatal thrombocytopenia is increased with:

- Mothers with a history of splenectomy for ITP

- Mothers who had a previous infant affected with ITP

- Gestational (maternal) platelet count less than 100,000/uL

It is recommended that pregnant women with thrombocytopenia or a previous diagnosis of ITP should be tested for serum antiplatelet antibodies. A woman with symptomatic thrombocytopenia and an identifiable antiplatelet antibody should be started on therapy for their ITP which may include steroids or IVIG. Fetal blood analysis to determine the platelet count is not generally performed as ITP-induced thrombocytopenia in the fetus is generally less severe than NAIT. Platelet transfusions may be performed in newborns, depending on the degree of thrombocytopenia. It is recommended that neonates be followed with serial platelet counts for the first few days after birth.,

In adults, particularly those living in areas with a high prevalence of "Helicobacter pylori" (which normally inhabits the stomach wall and has been associated with peptic ulcers), identification and treatment of this infection has been shown to improve platelet counts in a third of patients. In a fifth, the platelet count normalized completely; this response rate is similar to that found in treatment with rituximab, which is more expensive and less safe. In children, this approach is not supported by evidence, except in high prevalence areas. Urea breath testing and stool antigen testing perform better than serology-based tests; moreover, serology may be false-positive after treatment with IVIG.

Diagnosis is done by the help of symptoms and only blood count abnormality is thrombocytopenia.

The cardinal features of purpura investigations are the same as those of disseminated intravascular coagulation: prolonged plasma clotting times, thrombocytopenia, reduced plasma fibrinogen concentration, increased plasma fibrin-degradation products and occasionally microangiopathic haemolysis.

Multiple standards exist for defining Henoch–Schönlein purpura, including the 1990 American College of Rheumatology (ACR) classification and the 1994 Chapel Hill Consensus Conference (CHCC). Some have reported the ACR criteria to be more sensitive than those of the CHCC.

More recent classifications, the 2006 European League Against Rheumatism (EULAR) and Pediatric Rheumatology Society (PReS) classification, include palpable purpura as a mandatory criterion, together with at least one of the following findings: diffuse abdominal pain, predominant IgA deposition (confirmed on skin biopsy), acute arthritis in any joint, and renal involvement (as evidenced by the presence of blood and/or protein in the urine).

CBC and blood film: decreased platelets and schistocytes PT, aPTT, fibrinogen: normal Markers of hemolysis: increased unconjugated bilirubin, increased LDH, decreased haptoglobin Negative Coombs test

Creatinine, urea, to follow renal function ADAMSTS-13 gene, activity or inhibitor testing (TTP)

Laboratory tests for thrombocytopenia might include full blood count, liver enzymes, kidney function, vitamin B levels, folic acid levels, erythrocyte sedimentation rate, and peripheral blood smear. If the cause for the low platelet count remains unclear, a bone marrow biopsy is usually recommended to differentiate cases of decreased platelet production from cases of peripheral platelet destruction.

Thrombocytopenia in hospitalized alcoholics may be caused by spleen enlargement, folate deficiency, and, most frequently, the direct toxic effect of alcohol on production, survival time, and function of platelets. Platelet count begins to rise after 2 to 5 days' abstinence from alcohol. The condition is generally benign, and clinically significant hemorrhage is rare.

In severe thrombocytopenia, a bone marrow study can determine the number, size and maturity of the megakaryocytes. This information may identify ineffective platelet production as the cause of thrombocytopenia and rule out a malignant disease process at the same time.

The amount of fresh frozen plasma required to reverse disseminated intravascular coagulation associated with purpura fulminans may lead to complications of fluid overload and death, especially in neonates, such as transfusion-related acute lung injury. Exposure to multiple plasma donors over time increases the cumulative risk for transfusion-associated viral infection and allergic reaction to donor proteins found in fresh frozen plasma.

Allergic reactions and alloantibody formation are also potential complications, as with any protein replacement therapy.

Concomitant warfarin therapy in subjects with congenital protein C deficiency is associated with an increased risk of warfarin skin necrosis.

Henoch–Schönlein purpura may present with an atypical manifestation, which can be confused with papular urticaria, systemic lupus erythematosus, meningococcemia, dermatitis herpetiformis, and acute hemorrhagic edema of infancy.

The most rapidly effective treatment in infants with severe hemorrhage and/or severe thrombocytopenia (30,000 μL) an infusion of (1 g/kg/day for two days) in the infant has been shown to rapidly increase platelet count and reduce the risk of related injury.

After a first affected pregnancy, if a mother has plans for a subsequent pregnancy, then the mother and father should be typed for platelet antigens and the mother screened for alloantibodies. Testing is available through reference laboratories (such as ). testing of the father can be used to determine zygosiity of the involved antigen and therefore risk to future pregnancies (if homozygous for the antigen, all subsequent pregnancies will be affected, if heterozygous, there is an approximate 50% risk to each subsequent pregnancy). During subsequent pregnancies, the genotype of the fetus can also be determined using amniotic fluid analysis or maternal blood as early as 18 weeks gestation to definitively determine the risk to the fetus.

By tradition, the term idiopathic thrombocytopenic purpura is used when the cause is idiopathic. However, most cases are now considered to be immune-mediated.

Another form is thrombotic thrombocytopenic purpura.

Suggested diagnostic criteria for cryoglobulinemic disease fall into the following obligatory and additional categories:

- Obligatory criteria: 1) cold sensitivity; 2) cutaneous symptoms (i.e. urticaria, purpura, Raynaud phenomenon, ulceration/necrosis/gangrene, and/or livedo reticularis); 3) arterial and/or venous thrombotic events; fever; 4) arthralgia/myalgia; 5) neuritis in >1 site; and 6) renal disorder.

- Additional criteria: 1) typical biopsy findings at site(s) of involvement and 2) angiogram evidence of occlusion in one or more small to medium sized arteries.

The diagnosis of secondary cryofibrinogenemia also requires evidence for the cited infectious, malignant, premalignant vasculitis, and autoimmune disorders while the diagnosis of primary cryofibriongenemia requires a lack of evidence for 1) the cited associated disorders, 2) other vascular occlusive diseases, and 3) cryoglobulinemia.

Treatment of thrombotic thrombocytopenic purpura (TTP) is a medical emergency, since the associated hemolytic anemia and platelet activation can lead to renal failure and changes in the level of consciousness. Treatment of TTP was revolutionized in the 1980s with the application of plasmapheresis. According to the Furlan-Tsai hypothesis, this treatment works by removing antibodies against the von Willebrand factor-cleaving protease ADAMTS-13. The plasmapheresis procedure also adds active ADAMTS-13 protease proteins to the patient, restoring a normal level of von Willebrand factor multimers. Patients with persistent antibodies against ADAMTS-13 do not always manifest TTP, and these antibodies alone are not sufficient to explain how plasmapheresis treats TTP.

Drug-induced purpura is a skin condition that may be related to platelet destruction, vessel fragility, interference with platelet function, or vasculitis.

Immune thrombocytopenic purpura (), sometimes called idiopathic thrombocytopenic purpura is a condition in which autoantibodies are directed against a patient's own platelets, causing platelet destruction and thrombocytopenia. Anti-platelet autoantibodies in a pregnant woman with immune thrombocytopenic purpura will attack the patient's own platelets and will also cross the placenta and react against fetal platelets. Therefore, is a significant cause of fetal and neonatal immune thrombocytopenia. Approximately 10% of newborns affected by will have platelet counts <50,000 μL and 1% to 2% will have a risk of intracerebral hemorrhage comparable to infants with .

Mothers with thrombocytopenia or a previous diagnosis of should be tested for serum antiplatelet antibodies. A woman with symptomatic thrombocytopenia and an identifiable antiplatelet antibody should be started on therapy for their which may include steroids or . Fetal blood analysis to determine the platelet count is not generally performed as -induced thrombocytopenia in the fetus is generally less severe than . Platelet transfusions may be performed in newborns, depending on the degree of thrombocytopenia.

The course of treatment and the success rate is dependent on the type of TMA. Some patients with atypical HUS and TTP have responded to plasma infusions or exchanges, a procedure which replaces proteins necessary for the complement cascade that the patient does not have; however, this is not a permanent solution or treatment, especially for patients with congenital predispositions.

The diagnostic testing for vasculitis should be guided by the patient's history and physical exam. The clinician should ask about the duration, onset, and presence any associated symptoms such as weight loss or fatigue (that would indicate a systemic cause). It is important to distinguish between IgA and non-IgA vasculitis. IgA vasculitis is more likely to present with abdominal pain, bloody urine, and joint pain. In the case that the cause is not obvious, a reasonable initial workup would include a complete blood count, urinalysis, basic metabolic panel, fecal occult blood testing, erythrocyte sedimentation rate (ESR), and C-reactive protein level. Small vessel cutaneous vasculitis is a diagnosis of exclusion and requires ruling out systemic causes of the skin findings. Skin biopsy (punch or excisional) is the most definitive diagnostic test and should be performed with 48 hours of appearance of the vasculitis. A skin biopsy will be able to determine if the clinical findings are truly due to a vasculitis or due to some other cause.

Purpura are a common and nonspecific medical sign; however, the underlying mechanism commonly involves one of:

- Platelet disorders (thrombocytopenic purpura)

- Primary thrombocytopenic purpura

- Secondary thrombocytopenic purpura

- Post-transfusion purpura

- Vascular disorders (nonthrombocytopenic purpura)

- Microvascular injury, as seen in senile (old age) purpura, when blood vessels are more easily damaged

- Hypertensive states

- Deficient vascular support

- Vasculitis, as in the case of Henoch–Schönlein purpura

- Coagulation disorders

- Disseminated intravascular coagulation (DIC)

- Scurvy (vitamin C deficiency) - defect in collagen synthesis due to lack of hydroxylation of procollagen results in weakened capillary walls and cells

- Meningococcemia

- Cocaine use with concomitant use of the one-time chemotherapy drug and now veterinary deworming agent levamisole can cause purpura of the ears, face, trunk, or extremities, sometimes needing reconstructive surgery. Levamisole is purportedly a common cutting agent.

- Decomposition of blood vessels including purpura is a symptom of acute radiation poisoning in excess of 2 Grays of radiation exposure. This is an uncommon cause in general, but is commonly seen in victims of nuclear disaster.

Cases of psychogenic purpura are also described in the medical literature, some claimed to be due to "autoerythrocyte sensitization". Other studies suggest the local (cutaneous) activity of tissue plasminogen activator can be increased in psychogenic purpura, leading to substantial amounts of localized plasmin activity, rapid degradation of fibrin clots, and resultant bleeding. Petechial rash is also characteristic of a rickettsial infection.

A detailed history is important to elicit any recent medications, any risk of hepatitis infection, or any recent diagnosis with a connective tissue disorder such as systemic lupus erythematosus (SLE). A thorough physical exam is needed as usual.

- Lab tests. Basic lab tests may include a CBC, chem-7 (look for creatinine), muscle enzyme, liver function tests, ESR, hepatitis seroloties, urinalysis, CXR, and EKG. Additional, more specific tests include:

- Antinuclear antibody (ANA) test can detect an underlying connective tissue disorder, especially SLE

- Complement levels that are low can suggest mixed cryoglobulinemia, hepatitis C infection, and SLE, but not most other vasculitides.

- Antineutrophil cytoplasmic antibody (ANCA) may highly suggest granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, or drug-induced vasculitis, but is not diagnostic.

- Electromyography. It is useful if a systemic vasculitis is suspected and neuromuscular symptoms are present.

- Arteriography. Arteriograms are helpful in vasculitis affecting the large and medium vessels but not helpful in small vessel vasculitis. Angiograms of mesenteri or renal arteries in polyarteritis nodosa may show aneurysms, occlusions, and vascular wall abnormalities. Arteriography are not diagnostic in itself if other accessible areas for biopsy are present. However, in Takayasu's arteritis, where the aorta may be involved, it is unlikely a biopsy will be successful and angiography can be diagnostic.

- Tissue biopsy. This is the gold standard of diagnosis when biopsy is taken from the most involved area.

While the prognosis of cryofibrinoginemic disease varies greatly depending on its severity as well as the severity of its associated disorders, satisfactory clinical outcomes are reported in 50-80% of patients with primary or secondary disease treated with corticosteroid and/or immunosuppressive regimens. However, relapses occur within the first 6 months after stopping or decreasing therapy in 40-76% of cases. Sepsis resulting from infection of necrotic tissue is the most common threat to life in primary disease whereas the associated disorder is a critical determinant of prognosis in secondary disease.

Purpura is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin usually secondary to vasculitis or dietary deficiency of vitamin C (scurvy). They measure 0.3–1 cm (3–10 mm), whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm.

Purpura is common with typhus and can be present with meningitis caused by meningococci or septicaemia. In particular, meningococcus ("Neisseria meningitidis"), a Gram-negative diplococcus organism, releases endotoxin when it lyses. Endotoxin activates the Hageman factor (clotting factor XII), which causes disseminated intravascular coagulation (DIC). The DIC is what appears as a rash on the affected individual.

Nonthrombocytopenic purpura is a type of purpura (red or purple skin discoloration) not associated with thrombocytopenia.

Examples/causes include:

- Henoch–Schönlein purpura.

- Hereditary hemorrhagic telangiectasia

- Congenital cytomegalovirus

- Meningococcemia

Amyloid purpura affects a minority of individuals with amyloidosis. For example, purpura is present early in the disease in approximately 15% of patients with primary systemic amyloidosis.

The diagnosis is made upon blood tests to confirm not only hemolytic anemia and immune thrombocytopenic purpura, but also a positive direct antiglobulin test (DAT) and an absence of any known underlying cause.

Other antibodies may occur directed against neutrophils and lymphocytes, and "immunopancytopenia" has been suggested as a better term for this syndrome.

Amyloid purpura usually occurs above the nipple-line and is found in the webbing of the neck and in the face and eyelids.