Recognizing HAE is often difficult due to the wide variability in disease expression. The course of the disease is diverse and unpredictable, even within a single patient over their lifetime. This disease may be similar in its presentation to other forms of angioedema resulting from allergies or other medical conditions, but it is significantly different in cause and treatment. When hereditary angioedema is misdiagnosed as an allergy it is most commonly treated with steroids and epinephrine, drugs that are usually ineffective in treating a hereditary angioedema episode. Other misdiagnoses have resulted in unnecessary exploratory surgery for patients with abdominal swelling and other hereditary angioedema patients report that their abdominal pain was wrongly diagnosed as psychosomatic.

HAE accounts for only a small fraction of all cases of angioedema. To avoid potentially fatal consequences such as upper airway obstruction and unnecessary abdominal surgery, the importance of a correct diagnosis cannot be over-emphasized.

Consider hereditary angioedema (HAE) if a patient presents with:

- Recurrent angioedema (without urticaria)

- Recurrent episodes of abdominal pain and vomiting

- Laryngeal edema

- Positive family history of angioedema

A blood test, ideally taken during an episode, can be used to diagnose the condition. Measure: serum complement factor 4 (C4),

C1 inhibitor (C1-INH) antigenic protein, C1 inhibitor (C1-INH) functional level if available.Analysis of complement C1 inhibitor levels may play a role in diagnosis. C4 and C2 are complementary components.

The diagnosis is made on the clinical picture. Routine blood tests (complete blood count, electrolytes, renal function, liver enzymes) are typically performed. Mast cell tryptase levels may be elevated if the attack was due to an acute allergic (anaphylactic) reaction. When the patient has been stabilized, particular investigations may clarify the exact cause; complement levels, especially depletion of complement factors 2 and 4, may indicate deficiency of "C1-inhibitor". HAE type III is a diagnosis of exclusion consisting of observed angioedema along with normal C1 levels and function.

The hereditary form (HAE) often goes undetected for a long time, as its symptoms resemble those of more common disorders, such as allergy or intestinal colic. An important clue is the failure of hereditary angioedema to respond to antihistamines or steroids, a characteristic that distinguishes it from allergic reactions. It is particularly difficult to diagnose HAE in patients whose episodes are confined to the gastrointestinal tract. Besides a family history of the disease, only a laboratory analysis can provide final confirmation. In this analysis, it is usually a reduced complement factor C4, rather than the C1-INH deficiency itself, that is detected. The former is used during the reaction cascade in the complement system of immune defense, which is permanently overactive due to the lack of regulation by C1-INH.

Angioedema is classified as either hereditary or acquired.

Treatment with ACE inhibitors is contraindicated in this condition, as these drugs can lead to bradykinin accumulation, which can precipitate disease episodes.

In allergic angioedema, avoidance of the allergen and use of antihistamines may prevent future attacks. Cetirizine is a commonly prescribed antihistamine for angioedema. Some patients have reported success with the combination of a nightly low dose of cetirizine to moderate the frequency and severity of attacks, followed by a much higher dose when an attack does appear. Severe angioedema cases may require desensitization to the putative allergen, as mortality can occur. Chronic cases require steroid therapy, which generally leads to a good response. In cases where allergic attack is progressing towards airway obstruction, epinephrine may be life-saving.

It is estimated that 2—3 percent of hospitalised patients are affected by a drug eruption, and that serious drug eruptions occur in around 1 in 1000 patients.

Drug eruptions are diagnosed mainly from the medical history and clinical examination. However, they can mimic a wide range of other conditions, thus delaying diagnosis (for example, in drug-induced lupus erythematosus, or the acne-like rash caused by erlotinib). A skin biopsy, blood tests or immunological tests can also be useful.

Drug reactions have characteristic timing. The typical amount of time it takes for a rash to appear after exposure to a drug can help categorize the type of reaction. For example, Acute generalized exanthematous pustulosis usually occurs within 4 days of starting the culprit drug. Drug Reaction with Eosinophilia and Systemic Symptoms usually occurs between 15 and 40 days after exposure. Toxic epidermal necrolysis and Stevens-Johnson syndrome typically occur 7–21 days after exposure. Anaphylaxis occurs within minutes. Simple exanthematous eruptions occur between 4 and 14 days after exposure.

TEN and SJS are severe cutaneous drug reactions that involve the skin and mucous membranes. To accurately diagnose this condition, a detailed drug history is crucial. Often, several drugs may be causative and allergy testing may be helpful. Sulfa drugs are well-known to induce TEN or SJS in certain people. For example, HIV patients have an increased incidence of SJS or TEN compared to the general population and have been found to express low levels of the drug metabolizing enzyme responsible for detoxifying sulfa drugs. Genetics plays an important role in predisposing certain populations to TEN and SJS. As such, there are some FDA recommended genetic screening tests available for certain drugs and ethnic populations to prevent the occurrence of a drug eruption. The most well known example is carbamezepine (an anti-convulsant used to treat seizures) hypersensitivity associated with the presence of HLA-B*5801 genetic allele in Asian populations.

DIHS is a delayed onset drug eruption, often occurring a few weeks to 3 months after initiation of a drug. Interestingly, worsening of systemic symptoms occurs 3-4 days after cessation of the offending drug. There are genetic risk alleles that are predictive of the development of DIHS for particular drugs and ethnic populations. The most important of which is abacavir (an anti-viral used in the treatment of HIV) hypersensitivity associated with the presence of the HLA-B*5701 allele in European and African population in the United States and Australians.

AGEP is often caused by antimicrobial, anti-fungal or antimalarial drugs. Diagnosis is often carried out by patch testing. This testing should be performed within one month after resolution of the rash and patch test results are interpreted at different time points: 48 hours, 72hours and even later at 96 hours and 120 hours in order to improve the sensitivity.

When vWD is suspected, blood plasma of a patient must be investigated for quantitative and qualitative deficiencies of vWF. This is achieved by measuring the amount of vWF in a vWF antigen assay and the functionality of vWF with a glycoprotein (GP)Ib binding assay, a collagen binding assay, or a ristocetin cofactor activity (RiCof) or ristocetin induced platelet agglutination (RIPA) assays. Factor VIII levels are also performed because factor VIII is bound to vWF which protects the factor VIII from rapid breakdown within the blood. Deficiency of vWF can then lead to a reduction in factor VIII levels, which explains the elevation in PTT. Normal levels do not exclude all forms of vWD, particularly type 2, which may only be revealed by investigating platelet interaction with subendothelium under flow, a highly specialized coagulation study not routinely performed in most medical laboratories. A platelet aggregation assay will show an abnormal response to ristocetin with normal responses to the other agonists used. A platelet function assay may give an abnormal collagen/epinephrine closure time, and in most cases, a normal collagen/ADP time. Type 2N may be considered if factor VIII levels are disproportionately low, but confirmation requires a "factor VIII binding" assay. Additional laboratory tests that help classify sub-types of vWD include von-willebrand multimer analysis, modified ristocetin induced platelet aggregation assay and vWF propeptide to vWF antigen ratio propeptide. In cases of suspected acquired von-Willebrand syndrome, a mixing study study (analysis of patient plasma along with pooled normal plasma/PNP and a mixture of the two tested immediately, at one hour, and at two hours) should be performed. Detection of vWD is complicated by vWF being an acute phase reactant with levels rising in infection, pregnancy, and stress.

Other tests performed in any patient with bleeding problems are a complete blood count-CBC (especially platelet counts), activated partial thromboplastin time-APTT, prothrombin time with International Normalized Ratio-PTINR, thrombin time-TT, and fibrinogen level. Testing for factor IX may also be performed if hemophilia B is suspected. Other coagulation factor assays may be performed depending on the results of a coagulation screen. Patients with von Willebrand disease typically display a normal prothrombin time and a variable prolongation of partial thromboplastin time.

The testing for vWD can be influenced by laboratory procedures. Numerous variables exist in the testing procedure that may affect the validity of the test results and may result in a missed or erroneous diagnosis. The chance of procedural errors are typically greatest during the preanalytical phase (during collecting storage and transportation of the specimen) especially when the testing is contracted to an outside facility and the specimen is frozen and transported long distances. Diagnostic errors are not uncommon, and the rate of testing proficiency varies amongst laboratories, with error rates ranging from 7 to 22% in some studies to as high as 60% in cases of misclassification of vWD subtype. To increase the probability of a proper diagnosis, testing should be done at a facility with immediate on-site processing in a specialized coagulation laboratory.

Diagnosis of inherited hypoprothrombinemia, relies heavily on a patient's medical history, family history of bleeding issues, and lab exams performed by a hematologist. A physical examination by a general physician should also be performed in order to determine whether the condition is congenital or acquired, as well as ruling out other possible conditions with similar symptoms. For acquired forms, information must be taken regarding current diseases and medications taken by the patient, if applicable.

Lab tests that are performed to determine diagnosis:

1. Factor Assays: To observe the performance of specific factors (II) to identify missing/poorly performing factors. These lab tests are typically performed first in order to determine the status of the factor.

2. Prothrombin Blood Test: Determines if patient has deficient or low levels of Factor II.

3. Vitamin K1 Test: Performed to evaluate bleeding of unknown causes, nosebleeds, and identified bruising. To accomplish this, a band is wrapped around the patient's arm, 4 inches above the superficial vein site in the elbow pit. The vein is penetrated with the needle and amount of blood required for testing is obtained. Decreased vitamin K levels are suggestive of hypoprothrombinemia. However, this exam is rarely used as a Prothrombin Blood Test is performed beforehand.

Diagnosis of acquired dysfibrinogenemia uses the same laboratory tests that are used for congenital dysfibrinogenemia plus evidence for an underlying causative disease.

The cause of chronic hives can rarely be determined. In some cases regular extensive allergy testing over a long period of time is requested in hopes of getting new insight. No evidence shows regular allergy testing results in identification of a problem or relief for people with chronic hives. Regular allergy testing for people with chronic hives is not recommended.

A 28 month old girl, showed symptoms from 8 months of age and consisted of complaints of painful bruises over lower limbs, and disturbed, painful sleep at night. Family history revealed older brother also suffered similar problems and died at age of two years possibly due to bleeding - no diagnosis was confirmed. Complete blood count and blood smear was determined as normal. No abnormality in fibrinogen, liver function test, and bleeding time. However, prothrombin levels were less than 1% so patient was transfused with fresh frozen plasma (FFP). Post transfusion methods, patient is now 28 months old and living healthy life. The only treatment that is needed to date is for the painful bruises, which the patient is given FFP every 5-6 weeks.

Twelve day old boy admitted for symptoms consisting of blood stained vomiting and dark colored stool. Upon admission into hospital, patient received vitamin K and FFP transfusion. No family history of similarity in symptoms that were presented. At 40 days old, patient showed symptoms of tonic posturing and constant vomiting. CT scan revealed subdural hemorrhage, and other testing showed low hb levels of 7%, platelets at 3.5 lakhs/cu mm. PT examination was 51 seconds and aPTT at 87 seconds. Prothrombin activity levels were less than 1%. All other exams revealed no abnormalities. Treatment methods included vitamin K and FFP, as well as ventilator support and packed red blood cell transfusion (PRBC). At half a year of age, condition consisted of possible poor neurological outcome secondary to CNS bleeding. Treatment of very frequent transfusion was needed for patient.

Recent study illustrated a patient with 2 weeks of continuous bleeding, with presence of epistaxis, melena, hematuria, and pruritic rash with no previous bleeding history. Vitals were all within normal range, however, presence of ecchymoses was visible in chest, back and upper areas. Lab exams revealed prolonged prothrombin time (PT) of 34.4 and acquired partial thromboplastin time (aPTT) of 81.7, as well as elevated liver function tests. Discontinuation of atorvastatin, caused liver enzymes to go back to normal. Treatment of vitamin K, antibiotics, and fresh frozen plasma (FFP) did not have an impact on coagulopathy. Mixing of PT and aPTT was performed in order to further evaluate coagulopathy and revealed no correction. Factor activity assays were performed to determine the presence of a specific one. Testing revealed that factor II activity could not be quantified. Further studies showed that acquired factor II inhibitor was present without the lupus anticoagulant, with no clear cause associated with the condition. Aimed to control bleeding and getting rid of the inhibitor through directly treating the underlying disease or through immunosuppressive therapy. Corticosteroids and intravenous immunoglobulin improved the PT and aPTT. Did not improve bleeding conditions until treatment of transfusion with activated PCC. Treatment of inhibitor required Rituximab, which was shown to increase factor II levels to 264%. Study shows that when a patient with no history of coagulopathy presents themselves with hemorrhagic diathesis, direct testing of a factor II inhibitor should be performed initially.

Treatment of asymptomatic congenital dysfibrinogenemia depends in part on the expectations of developing bleeding and/or thrombotic complications as estimated based on the history of family members with the disorder and, where available, determination of the exact mutation causing the disorder plus the propensity of the particular mutation type to develop these complications. In general, individuals with this disorder require regular follow-up and multidiscipline management prior to surgery, pregnancy, and giving childbirth. Women with the disorder appear to have an increased rate of miscarriages and all individuals with fibrinogen activity in clotting tests below 0.5 grams/liter are prone to bleeding and spontaneous abortions. Women with multiple miscarriages and individuals with excessively low fibrinogen activity levels should be considered for prophylaxis therapy with fibrinogen replacement during pregnancy, delivery, and/or surgery.

Drug-induced angioedema is a known complication of the use of angiotensin-converting enzyme (ACE) inhibitors, angiotensin II antagonists (ARBs), and Angiotensin-Neprilysin Inhibitor LCZ969. The angioedema appears to be dose dependent as it may resolve with decreased dose.

Some common ACE Inhibitors are:

- Benazepril (Lotensin)

- Captopril (Capoten)

- Enalapril (Vasotec)

- Lisinopril (Prinivil, Zestril)

- Ramipril (Altace)

Some common ARBs are:

- Candesartan (Atacand)

- Losartan (Cozaar)

- Olmesartan (Benicar)

- Valsartan (Diovan)

Angioedema presents itself as an abrupt onset of non-pitting, non-itchy swelling that involves the mucosal layers. Some common locations of angioedema are the face, particularly the lips and around the eyes, hands and feet, and genitalia. A rare, yet serious complication is one inside the abdomen, the symptom usually being severe stomach upset, which is much less obvious than the other locations.

The chance of drug-induced angioedema is extremely uncommon, however, as studies show incidence of less than 1%. The reason this adverse effect may occur is due to the build-up of bradykinin, a vasodilator. This causes blood vessels to dilate and allow for fluid buildup in the mucosal surfaces.

Angioedema is similar to hives, but in angioedema, the swelling occurs in a lower layer of the dermis than in hives, as well as in the subcutis. This swelling can occur around the mouth, eyes, in the throat, in the abdomen, or in other locations. Hives and angioedema sometimes occur together in response to an allergen, and is a concern in severe cases, as angioedema of the throat can be fatal.

The four hereditary types of vWD described are type 1, type 2, type 3, and pseudo- or platelet-type. Most cases are hereditary, but acquired forms of vWD have been described. The International Society on Thrombosis and Haemostasis's classification depends on the definition of qualitative and quantitative defects.

MCAS is often difficult to identify due to the heterogeneity of symptoms and the "lack of flagrant acute presentation." The condition can also be difficult to diagnose, especially since many of the numerous symptoms may be considered "vague". Patients often see many different specialties due to the inherent multisystem nature of the condition, and do not get diagnosed until a holistic view is taken by a diagnostician. Lack of awareness of MCAS by many medical professionals is currently a hurdle to proper diagnosis.

1. Symptoms consistent with chronic/recurrent mast cell release: Recurrent abdominal pain, diarrhea, flushing, itching, nasal congestion, coughing, chest tightness, wheezing, lightheadedness (usually a combination of some of these symptoms is present)

2. Laboratory evidence of mast cell mediator (elevated serum tryptase, N-methyl histamine, prostaglandin D2 or 11-beta- prostaglandin F2 alpha, leukotriene E4 and others)

3. Improvement in symptoms with the use of medications that block or treat elevations in these mediators"

The World Health Organization has not published diagnostic criteria.

There is no cure for MCAS. For most, symptoms wax and wane, but many can experience a general worsening trend over time. Lifespan for those with MCAS appears to be normal, but quality of life can range from mild discomfort to severely impaired. Some patients are impaired enough to be disabled and unable to work.

The term morbilliform refers to a rash that looks like measles. The rash consists of macular lesions that are red and usually 2–10 mm in diameter but may be confluent in places.

Patients with measles will have the rash but there are other syndromes and infections that will display the same symptom such as patients with Kawasaki disease, meningococcal petechiae or Waterhouse-Friderichsen syndrome, Dengue, congenital syphilis, rubella, Echovirus 9, drug hypersensitivity reactions (in particular with certain classes of antiretroviral drugs, such as abacavir and nevirapine, and also the antiepileptic drug phenytoin), or other conditions may also have a morbilliform rash.

One cause of morbilliform rash is an allergic reaction to transfused blood/blood components. In such a case, the skin lesions would develop within a few hours (Approx. 4hours) of transfusion along with pruritus. The condition may even present with other symptoms, such as conjunctival oedema, oedema in the lips and tongue, and even localised angioedema. On rare occasions, the condition may even escalate to anaphylactic shock where pulmonary restrictions are seen. The associated cause for this is a reaction against an allergen that is seldom identified during testing. Transfusing products with anti-IgA antibodies to IgA-deficient patients has also been a suspected cause for such reactions. Management usually relates to the stoppage of transfusion for around 30minutes, until given antihistamines take effect. Transfusion may even be continued after, if no further progression is seen.

The basic tests performed when an immunodeficiency is suspected should include a full blood count (including accurate lymphocyte and granulocyte counts) and immunoglobulin levels (the three most important types of antibodies: IgG, IgA and IgM).

Other tests are performed depending on the suspected disorder:

- Quantification of the different types of mononuclear cells in the blood (i.e. lymphocytes and monocytes): different groups of T lymphocytes (dependent on their cell surface markers, e.g. CD4+, CD8+, CD3+, TCRαβ and TCRγδ), groups of B lymphocytes (CD19, CD20, CD21 and Immunoglobulin), natural killer cells and monocytes (CD15+), as well as activation markers (HLA-DR, CD25, CD80 (B cells).

- Tests for T cell function: skin tests for delayed-type hypersensitivity, cell responses to mitogens and allogeneic cells, cytokine production by cells

- Tests for B cell function: antibodies to routine immunisations and commonly acquired infections, quantification of IgG subclasses

- Tests for phagocyte function: reduction of nitro blue tetrazolium chloride, assays of chemotaxis, bactericidal activity.

Due to the rarity of many primary immunodeficiencies, many of the above tests are highly specialised and tend to be performed in research laboratories.

Criteria for diagnosis were agreed in 1999. For instance, an antibody deficiency can be diagnosed in the presence of low immunoglobulins, recurrent infections and failure of the development of antibodies on exposure to antigens. The 1999 criteria also distinguish between "definitive", "probable" and "possible" in the diagnosis of primary immunodeficiency. "Definitive" diagnosis is made when it is likely that in 20 years, the patient has a >98% chance of the same diagnosis being made; this level of diagnosis is achievable with the detection of a genetic mutation or very specific circumstantial abnormalities. "Probable" diagnosis is made when no genetic diagnosis can be made, but the patient has all other characteristics of a particular disease; the chance of the same diagnosis being made 20 years later is estimated to be 85-97%. Finally, a "possible" diagnosis is made when the patient has only some of the characteristics of a disease are present, but not all.

There are three main classifications of anaphylaxis. Anaphylactic shock is associated with systemic vasodilation that causes low blood pressure which is by definition 30% lower than the person's baseline or below standard values. Biphasic anaphylaxis is the recurrence of symptoms within 1–72 hours with no further exposure to the allergen. Reports of incidence vary, with some studies claiming as many as 20% of cases. The recurrence typically occurs within 8 hours. It is managed in the same manner as anaphylaxis. Pseudoanaphylaxis or anaphylactoid reactions are a type of anaphylaxis that does not involve an allergic reaction but is due to direct mast cell degranulation. Non-immune anaphylaxis is the current term used by the World Allergy Organization with some recommending that the old terminology no longer be used.

The life span in patients with Schnitzler syndrome has not been shown to differ much from the general population. Careful follow-up is advised, however. A significant proportion of patients develops a lymphoproliferative disorder as a complication, most commonly Waldenström's macroglobulinemia. This may lead to symptoms of hyperviscosity syndrome. AA amyloidosis has also been reported in people with Schnitzler syndrome.

In a person who died from anaphylaxis, autopsy may show an "empty heart" attributed to reduced venous return from vasodilation and redistribution of intravascular volume from the central to the peripheral compartment. Other signs are laryngeal edema, eosinophilia in lungs, heart and tissues, and evidence of myocardial hypoperfusion. Laboratory findings could detect increased levels of serum tryptase, increase in total and specific IgE serum levels.

Gleich's syndrome or episodic angioedema with eosinophilia is a rare disease in which the body swells up episodically (angioedema), associated with raised antibodies of the IgM type and increased numbers of eosinophil granulocytes, a type of white blood cells, in the blood (eosinophilia). It was first described in 1984.

Its cause is unknown, but it is unrelated to capillary leak syndrome (which may cause similar swelling episodes) and eosinophilia-myalgia syndrome (which features eosinophilia but alternative symptoms). Some studies have shown that edema attacks are associated with degranulation (release of enzymes and mediators from eosinophils), and others have demonstrated antibodies against endothelium (cells lining blood vessels) in the condition.

Gleich's syndrome is not a form of the idiopathic hypereosinophilic syndrome in that there is little or no evidence that it leads to organ damage. Rather, recent studies report that a subset of T cells (a special form of lymphocyte blood cell) found in several Gleich syndrome patients have an abnormal immunophenotype, i.e. they express CD3-, CD4+ cluster of differentiation cell surface antigens. These same aberrant T cell immunophenotypes are found in lymphocyte-variant eosinophilia, a disease in which the aberrant T cells overproduce cytokines such as interleukin 5 which simulate the proliferation of eosinophil precursor cells and are thereby responsible for the eosinophilia. It is suggested that most forms of Gleich's syndrome are due to a similar aberrant T cell mechanism and are a subtype of lymphocyte-variant eosinophilia.

Gleich syndrome has a good prognosis. Attack severity may improve with steroid treatment.

The current (2008) diagnostic criteria for HLH are

1. A molecular diagnosis consistent with HLH. These include the identification of pathologic mutations of PRF1, UNC13D, or STX11.

OR

2. Fulfillment of five out of the eight criteria below:

- Fever (defined as a temperature >100.4 °F, >38 °C)

- Enlargement of the spleen

- Decreased blood cell counts affecting at least two of three lineages in the peripheral blood:

- Haemoglobin <9 g/100 ml (in infants <4 weeks: haemoglobin <10 g/100 ml) (anemia)

- Platelets <100×10/L (thrombocytopenia)

- Neutrophils <1×10/L (neutropenia

- High blood levels of triglycerides (fasting, greater than or equal to 265 mg/100 ml) and/or decreased amounts of fibrinogen in the blood (≤ 150 mg/100 ml)

- Ferritin ≥ 500 ng/ml

- Haemophagocytosis in the bone marrow, spleen or lymph nodes

- Low or absent natural killer cell activity

- Soluble CD25 (soluble IL-2 receptor) >2400 U/ml (or per local reference laboratory)

In addition, in the case of familial HLH, no evidence of malignancy should be apparent.

It should be noted that not all five out of eight criteria are required for diagnosis of HLH in adults, and a high index of suspicion is required for diagnosis as delays results in increased mortality. The diagnostic criteria were developed in pediatric populations and have not been validated for adult HLH patients. Attempts to improve diagnosis of HLH have included use of the HScore, which can be used to estimate an individual's risk of HLH.

The treatment of primary immunodeficiencies depends foremost on the nature of the abnormality. Somatic treatment of primarily genetic defects is in its infancy. Most treatment is therefore passive and palliative, and falls into two modalities: managing infections and boosting the immune system.

Reduction of exposure to pathogens may be recommended, and in many situations prophylactic antibiotics or antivirals may be advised.

In the case of humoral immune deficiency, immunoglobulin replacement therapy in the form of intravenous immunoglobulin (IVIG) or subcutaneous immunoglobulin (SCIG) may be available.

In cases of autoimmune disorders, immunosuppression therapies like corticosteroids may be prescribed.