Hereditary angioedema (HAE) encompasses a group of diseases characterized by recurrent, genetically mediated angioedema associated with increased vascular permeability primarily due to bradykinin. The disease poses diagnostic challenges, leading to underdiagnosis and delayed therapy. Severe manifestations include laryngeal and intestinal angioedema, contributing to significant morbidity and mortality. If left undiagnosed, the estimated mortality rate of the disease ranges from 25% to 40% due to asphyxiation caused by laryngeal angioedema. There is a pressing need to enhance awareness of hereditary angioedema and its warning signs. The acronym \"H4AE\" may facilitate the memorization of these signs. This study comprehensively reviews clinical, laboratory, and physiopathological features of documented HAE subtypes. The study advocates for an improved HAE classification based on endotypes, building on the knowledge of angioedema pathophysiology. The proposed endotype classification of HAE offers a clear and applicable framework, encouraging advancements in disease understanding and classification.

Angioedema is a rare but known side effect of angiotensin-converting enzyme (ACE) inhibitor therapy. The most common presentations of ACE inhibitor-induced angioedema describe swellings in the oropharyngeal and periorbital regions. We describe a rare case of a 58-year-old female with a history of type 2 diabetes and hypertension taking lisinopril for the past three years and presented with recurrent episodes of abdominal pain, nausea, and vomiting around the same time she started taking the drug. Multiple computed tomography (CT) scans were performed, which showed findings consistent with edema in the proximal small bowel. Due to the recurrent nature of these episodes over the last three years, along with consistent findings of small bowel edema on imaging, lisinopril-induced angioedema was suspected. As a result, the patient was switched from lisinopril to amlodipine. During our follow-up with the patient, she reported that her symptoms had resolved following the withdrawal of lisinopril.

The following describes a case of isolated visceral angioedema related to an angiotensin II receptor blocker (ARB) medication. Additionally, we discuss the pathophysiology of drug-induced angioedema, various presentations that can be encountered, and the leading theorized mechanisms of how renin-angiotensin-aldosterone system (RAAS) blocking medications lead to angioedema. The goal of sharing this case is to help increase awareness of the possibility of ARB-induced angioedema and to recommend keeping visceral angioedema as part of the differential diagnosis when presented with a patient who is taking an angiotensin converting enzyme inhibitor (ACEI) or ARB medication that is experiencing gastrointestinal symptoms of unclear etiology.

Angioedema with evidence of mucosal swelling is a rare condition that can be caused by angiotensin-converting enzyme inhibitors. The authors describe a case of a 28-year-old woman medicated with lisinopril 2 months before, with abdominal pain associated with nausea, vomiting and a onetime watery stool. A small volume of ascites was found in the abdominal ultrasound and the parietal thickening of the middle ileum in the abdominal computed tomography (CT). The complementary study was negative. The symptoms stopped after drug withdrawal. The authors intend to warn to this diagnosis, which has non-specific symptoms and if not suspected, can lead to a great morbidity for patients. The authors also intend to identify various signs that can be clues for its correct diagnosis.

A 75-year-old woman presented with recurrent abdominal pain and vomiting for 1 year and was later found to have splenomegaly and pancytopenia. This case report depicts a clinical picture of intestinal angioedema, a challenging diagnosis, and an underlying rare syndrome of acquired C1 esterase inhibitor deficiency associated with splenic marginal zone lymphoma.

Angioedema can be either mast cell-(histamine-)mediated or bradykinin-mediated. Treatment approaches for the two types are very different, making differential diagnosis critical. Severe acute abdominal pain caused by intestinal angioedema is commonly misdiagnosed, especially when associated with bradykinin-mediated angioedema. After describing a typical clinical scenario and diagnostic journey of a patient with recurrent, undiagnosed abdominal pain due to hereditary angioedema (HAE), a rare variant of bradykinin-mediated angioedema, we delve into the classification and differential diagnosis of the various types of angioedema and provide an overview of appropriate management with an emphasis on the bradykinin-mediated types. Bradykinin-induced angioedema may be inherited or acquired and is infrequent compared to mast cell-mediated angioedema. HAE is a rare disease characterized by recurrent attacks of non-urticarial, nonpruritic edema usually affecting the face, respiratory tract, extremities, gastrointestinal tract, and genitalia. Unlike mast cell-mediated angioedema, painful abdominal symptoms are prevalent in bradykinin-mediated angioedema and are sometimes the only manifestation of an attack, increasing the likelihood of initial misdiagnosis as appendicitis or other forms of acute abdomen. It is important for gastroenterologists to be vigilant for the possibility of angioedema pathology in patients presenting with undiagnosed, recurrent, abdominal symptoms to facilitate accurate diagnosis and effective treatment.

Intestinal angioedema is a rare side effect of angiotensin-converting enzyme inhibitors. We present a 41-year-old woman with sporadic right lower quadrant abdominal pain and diarrhea with multiple computed tomography scans demonstrating enteritis. Suspicion turned to angiotensin-converting enzyme inhibitor use as the cause for the patient\'s illness after an extensive negative evaluation including labs, stool studies, endoscopies, and capsule endoscopy. Weeks after stopping the medication, the patient\'s symptoms improved and repeat computed tomography showed a resolution of the previously seen findings of enteritis. This case illustrates the importance of a good medication review to make appropriate clinical decisions and diagnoses.

Angiotensin-converting enzyme inhibitor induced angioedema commonly involves the head and neck area. We report a case of angiotensin-converting enzyme inhibitor induced intestinal angioedema in a heart transplant recipient on mTOR immunosuppression. A 36-year-old Caucasian woman with history of heart transplantation on sirolimus, tacrolimus and prednisone presented to the Emergency Department with abdominal pain, one day following lisinopril initiation. A computer tomography scan demonstrated diffuse bowel wall thickening consistent with pancolitis and edema. She was subsequently diagnosed with angiotensin-converting enzyme inhibitor induced angioedema. Patients on mTOR immunosuppression are at higher risk for this potentially life-threatening side effect. Knowledge of this interaction is critical for providers prescribing mTOR agents.

A 42-year-old woman presents with abdominal pain after taking her first dose of lisinopril. Visceral angioedema was diagnosed based on clinical suspicion and abdominal computed tomography (CT). Awareness of this rare side effect of a common medication is key to avoid delays in diagnosis and unnecessary procedures.

BACKGROUND: Angioedema is a condition that can cause cutaneous and mucosal edema of practically any part of the body. Isolated edema of the intestines is a rather rare manifestation, but it can cause important morbidity. Hereditary angioedema as well as certain medications can give rise to intestinal angioedema. We have seen a rise in frequency of intestinal angioedema since the advent of angiotensin-converting enzyme inhibitors. Ultrasound of the abdomen is an inexpensive, safe, and easy tool that can help in the differential diagnosis.
METHODS: We describe the case of a 25-year-old woman who presented with acute abdominal pain. She was diagnosed with intestinal angioedema due to hereditary angioedema type I. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Misdiagnosis can lead to administering the wrong treatment or even unnecessary surgical interventions. Intestinal angioedema is best treated with purified C1-inhibitor, icatibant, or ecallantide. Fresh frozen plasma is to be avoided because it carries the risk of worsening the symptoms.