This chapter describes normal erythroid maturation and the dynamic antigenic changes during erythroid differentiation. Common markers used to define the erythroid lineage are discussed, with their advantages and limitations included. Key immunophenotypic features associated with erythroid aberrancies are highlighted. For acute erythroid leukemia, three subtypes and their immunophenotypic profiles are described. Finally, the differential diagnosis of AEL is addressed.

This is a clinical presentation of a patient with chest pain. The candidate is challenged with the task of correctly diagnosing and treating a pulmonary embolus. This is relevant to emergency medicine residents preparing for the oral and written board exams. This would also be helpful for medical students preparing for the emergency medicine shelf exam.

This chapter reviews a case of weakness from ischemic stroke. It engages the reader by presenting the patient and asking the reader the various steps needed to manage, identify, and treat the stroke.

This chapter introduces the classification of acute myeloid leukemia (AML) and highlights the importance of integrating both genetic and immunophenotypic findings in the diagnostic process. AML blasts exhibit a diverse range of immunophenotypic profiles, and key markers associated with each immunophenotypic subtype are discussed. The assessment of minimal residual disease (MRD) is crucial in AML, as it provides important information regarding treatment response and prognosis. Both flow cytometry and molecular testing are used in MRD evaluation.

This chapter discusses the presentation, diagnostics, and management of necrotizing fasciitis. Necrotizing fasciitis has a high mortality rate. Readers will understand that early recognition of the diagnosis is critical and that they should not rely on the presence or absence of gas on imaging in their diagnostics. Necrotizing fasciitis is a surgical emergency, requiring IV antibiotics, aggressive fluid resuscitation, and immediate surgical intervention. Surgery consultation should not be delayed to obtain advanced imaging.

This chapter presents a case of a 64-year-old male with hypercalcemia due to squamous cell lung cancer. The case highlights the approach to the identification of a hypercalcemic state, as well as the appropriate medical interventions to prevent progression and deterioration to a comatose state.

There are three subtypes of T-prolymphocytic leukemia (T-PLL) based on their cytogenetic presentations, all of which share a similar immunophenotype. This chapter discuss their immunophenotype in detail. Occasional cases with atypical immunophenotypes, such as negative CD3 or CD45 expression, are also described. Tumor heterogeneity, with populations displaying different immunophenotypes, is discussed, along with immunophenotypic shift. Differential diagnosis is addressed, with a focus on the challenges in distinguishing TCL1-family negative T-PLL from other leukemic T-cell lymphomas/leukemias.

Neoplasms derived from plasma cells are collectively termed plasma cell neoplasms (PCNs), the most notable of which is multiple myeloma. Neoplastic plasma cells in PCNs have distinct immunophenotypes that differ from normal plasma cells and those associated with B-cell lymphoma. Thus flow cytometry can be used to identify aberrant plasma cells to facilitate diagnosis and to monitor treatment response, such as minimal residual (measurable) disease. In addition, flow cytometry is instrumental in differentiating plasma cell neoplasms from B-cell lymphomas with plasmacytic differentiation, such as lymphoplasmacytic lymphoma or marginal zone lymphoma. This distinction is of critical importance in terms of clinical treatment and prognosis. This chapter focuses on the applications of flow cytometry in characterizing the immunophenotypic features of plasma cell neoplasms and their key distinctions from B-cell lymphomas and other diagnostic challenges.

This case demonstrates the emergency medicine approach to evaluating a patient with a painful foot and a diagnosis of acute gout. Key components of the history include timing, location, number of joints involved, pertinent past medical history, and any precipitating factors. A focused physical exam reveals swelling and erythema overlying the first MTP joint of the foot with painful range of motion, consistent with a diagnosis of acute gout. Key interventions include joint aspiration to rule out septic arthritis, revealing negatively birefringent crystals; and appropriate medication treatment with NSAIDs as first-line therapy, followed by colchicine or oral steroids. Patients should receive counseling regarding dietary guidelines and follow-up, with consideration of long-term treatment in cases of recurrence.

This chapter discusses a five-month-old female who presents with a three-week history of a cough. This patient is woken at night by her cough and has multiple “coughing fits” throughout the day that subsequently result in post-tussive emesis. Her exam is only significant for a left subconjunctival hemorrhage and diffuse rhonchi throughout her lungs without any retractions or tachypnea. Her labs are significant for a large leukocytosis. She has a normal chest x-ray. During her course in the ED, she has an episode of apnea associated with cyanosis that resolved without intervention. This presentation is classic for pertussis in an infant child. Pertussis is caused by the gram-negative bacteria Bordetella pertussis. Patients with this condition typically present with cough paroxysms that is followed by a characteristic “whoop” and vomiting. The course of pertussis is characterized by three different phases: the catarrhal phase, the paroxysmal phase, and the convalescent phase. Diagnosis is based on clinical criteria and confirmatory labs such as a culture isolate of B. pertussisobtained from a throat swab or aspirate or a positive PCR. Treatment is typically a five-day course of azithromycin and is most effective early in the course of the disease.

Perforated viscus presents a life-threatening emergency requiring immediate clinical recognition and swift medical and surgical intervention. In this scenario, perforation likely arises from small bowel obstruction, causing increased intraabdominal pressure and subsequent wall rupture. Symptoms include sudden-onset abdominal pain worsened by movement. Urgent actions include focused physical assessment, detection of peritoneal signs, IV fluid resuscitation, pain management, selection of appropriate imaging, early antibiotic administration, surgical consultation, and advocating for laparotomy. Key points emphasize the superiority of upright CXR for free-air detection, the significance of peritoneal signs, and the crucial importance of timely evaluation in elderly patients with abdominal pain.

The chapter describes a case of a 46-year-old male brought in by EMS on a backboard and cervical collar with spinal immobilization after being involved in a high-speed motor vehicle collision. The patient complains of abdominal pain and has a history of hypertension. The primary survey reveals cool and clammy skin, normal capillary refill, and increased respiratory rate. The patient is given two large-bore peripheral IV lines and CBC, BMP, LFT, coagulation studies, and blood type labs are conducted. The patient is diagnosed with splenic rupture from blunt abdominal trauma. The critical actions include obtaining large-bore IV line access, administering initial IV fluid challenge, performing a FAST examination including thoracic views, early pRBC infusion once hemorrhage is recognized, early trauma surgery involvement, pain control, and advocating for laparotomy given the patient decompensates twice with CT findings of splenic rupture. The chapter provides pearls on the management of splenic injury and the lethal triad of hypothermia, coagulopathy, and acidosis.

This case study presents a classic example of acute mesenteric ischemia caused by an embolism to the superior mesenteric artery in a 73-year-old female. The patient exhibits sudden-onset severe abdominal pain disproportionate to physical findings, with a history suggestive of atrial fibrillation. The diagnostic work-up includes CT angiography revealing a thrombus and bowel ischemia. Management involves fluid resuscitation, broad-spectrum antibiotics, anticoagulation with intravenous heparin, and surgical consultation. The case emphasizes the importance of early recognition and intervention in mesenteric ischemia, a condition with high mortality if untreated.

Care of the patient with traumatic injuries begins with the ABCs. Airway must be secured before proceeding with other evaluation and treatment. Penetrating chest trauma can cause a pericardial effusion and cardiac tamponade. Recognition of pericardial effusion and diagnosis of cardiac tamponade is an imperative skill for the emergency physician. Identifying Beck’s triad of hypotension, distended neck veins, and muffled heart sounds can assist in the diagnosis of cardiac tamponade. Bedside ultrasound and the eFAST exam can confirm the diagnosis. On a cardiac view of the eFAST, pericardial effusion appears as an anechoic or hypoechoic stripe between the visceral and parietal layers of the pericardium. Tamponade is the collapse of the right ventricle during diastole, preventing filling of the heart. Traumatic pericardial effusions are typically caused by bleeding into the pericardium. Initial treatment of cardiac tamponade begins with fluid resuscitation, thus increasing preload capacity. Needle pericardiocentesis of traumatic pericardial effusions are temporizing measures, as blood quickly reaccumulates into the pericardium. Cardiac arrest may occur due to cardiac tamponade. ED thoracotomy should be performed to directly tamponade bleeding from the ventricle, and surgery should be consulted to take the patient to the OR for definitive repair.

This chapter discusses the immunophenotypic features of adult and pediatric follicular lymphoma (FL), including those with atypical immunophenotypes such as CD5+ or CD10−. The differential diagnosis includes CD10+ non-neoplastic but monotypic B-cell processes and CD10+ B-cell lymphomas/leukemias other than FL.

This chapter delves into the narrative aspect of emergency medicine, highlighting the importance of storytelling in patient care and the oral board examination process. It discusses the structured nature of the oral examination, which combines elements of an Observed Structured Clinical Encounter (OSCE) and simulation to evaluate candidates’ clinical skills. The chapter provides insights into the virtual platform used for the exam, the unfolding of cases, and the examiner’s role in guiding the narrative. Strategies for approaching cases, organizing information, and interacting with examiners are detailed, emphasizing the need for efficient data collection and clear communication. Practical tips for exam preparation, including technology setup, time management, and professional conduct, are outlined to help candidates navigate the challenging oral board experience. The structured interview component is also explored, focusing on critical thinking and decision-making processes. Differences between the American Board of Emergency Medicine (ABEM) and the American Osteopathic Board of Emergency Medicine (AOBEM) exams are discussed, with a glimpse into the future transition to an in-person certifying exam by ABEM in 2026.

This chapter presents a case of a 73-year-old female with neurologic deficits as a result of hypoglycemia secondary to not eating breakfast after taking glyburide. The case highlights the importance of obtaining an immediate blood glucose level in making the diagnosis and further action beyond the rapid correction of blood glucose with dextrose and maintenance of blood sugar levels because sulfonylurea drugs can cause rebound hypoglycemia for many hours.

Mature B-cell lymphomas can exhibit considerable plasmacytic differention, the most typical examples of which are lymphoplasmcytic lymphoma (LPL) and marginal zone lymphoma (MZL). The degree of plasmacytic differentiation can sometimes blur the lines between a B-cell lymphoma and a plasma cell neoplasm by morphology or immunohistochemistry. However, characteristic immunophenotypic features by flow cytometry can facilitate this distinction, which is of particular importance for clinical management. This chapter focuses on the applications of flow cytometry in characterizing the immunophenotypic features of LPL and MZL and their key distinctions from each other, plasma cell neoplasms, and other diagnostic challenges.

Systemic mastocytosis (SM) is characterized by clonal proliferation of mast cells in extracutaneous tissue. This chapter focuses on the immunophenotypic features of SM and the differences among SM subtypes. The methodology for testing and analyzing mast cells by flow cytometry is introduced, including panel design and gating strategies. The differential diagnosis of SM is also discussed, with a focus on flow cytometric findings, including normal/reactive mast cells, basophils, acute myeloid leukemia with mast cell differentiation, and myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions. Flow cytometric immunophenotypic features that can be helpful for the differential diagnosis are discussed.