Recognizing<unk>  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<unk>  resulting from allergies or other medical conditions, but it is significantly different in cause and treatment. When<unk>  is misdiagnosed as an allergy it is most commonly treated with steroids and epinephrine, drugs that are usually ineffective in treating a<unk>  episode. Other misdiagnoses have resulted in unnecessary exploratory surgery for patients with abdominal swelling and other<unk>  patients report that their abdominal pain was wrongly diagnosed as psychosomatic.<unk>  accounts for only a small fraction of all cases of<unk> . To avoid potentially fatal consequences such as upper airway obstruction and unnecessary abdominal surgery, the importance of a correct diagnosis cannot be over-emphasized.<unk>  should be considered if a patient presents with: * Recurrent<unk>  (without urticaria) * Recurrent episodes of abdominal pain and vomiting * Laryngeal edema * Positive family history of<unk>  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. Types There are three types of C1 inhibitor deficiency:<unk>  type I is primarily caused by a deficiency in blood proteins (C1 esterase inhibitors) which normally suppress activation of the complement system. The resultant over-stimulation of this system leads to the production of inflammatory anaphylatoxins, which affects the flow of body fluids between the vascular system and body tissues. This deficiency is responsible for approximately 80–85% of cases.<unk>  type II is a less frequently encountered form of this disorder and accounts for 15–20% of cases. In this type, atypical C1-inhibitor proteins are produced which are less capable of suppressing activation of the complement system. Like<unk>  type I, this results in over-stimulation of this system.<unk>  type III is rare and has only been documented recently. Unlike types I and II, this form does not appear to be connected with C1-inhibitor deficiency. This type mainly affects females and appears to be influenced by contact with estrogens and also by hormone replacement therapy (e.g. oral contraceptives). Its pathogenesis is credited to increased activity of the enzyme kininogenase, which leads to rise in the levels of bradykinin. Other patients with type III<unk>  have alterations in gene F12, which encodes a protein which participates in blood coagulation. Some patients with type III<unk>  have a mutation in the F12 gene which produces a protein involved in blood clotting. Due to the results of a genetic test on 4 affected German families, it is believed that this type of the condition is caused by a disease-causing gene in chromosome 5q.35.2-q35.3.
Hereditary angioedema
Bowel obstruction
Drug-induced angioedema
Angioedema
Oral allergy syndrome
Acquired C1 esterase inhibitor deficiency
Rice allergy
Drug-induced urticaria