Sarcoidosis – Top USMLE Diseases

Pneumonia is the infection of the lung parenchyma, resulting from the spread of pathogens and accompanied by the host inflammatory response. This condition is the most common infectious cause of death. Multiple organisms cause pneumonia, including bacteria (of which Streptococcus pneumoniae is the most common), viruses, and fungi. The infection can be acquired while hospitalized (hospital-acquired) or outside the hospital setting (community-acquired). Common symptoms include fever, chills, cough, chest pain, and dyspnea. Chest X-ray usually shows consolidation and/or infiltrates. Diagnosis can be made with clinical presentation and imaging, but in severe cases, microbiological testing (sputum and cultures, molecular testing) and routine blood tests are needed. Empiric treatment with antibiotics is recommended, with regimen depending on the setting, risk factors for multidrug-resistant organisms, and individual comorbidities. Identification of the causative pathogen helps narrow down the antibiotics. Preventive measures include vaccinations (pneumococcal and influenza) and smoking cessation.

Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. The classification and phenotypes are heterogeneous but mainly divided into T2-high (inflammatory with eosinophils) and T2-low (noninflammatory) asthma. Patients typically present with wheezing, cough, and dyspnea. Diagnosis is confirmed with pulmonary function testing showing a reversible obstructive pattern. Treatment, based on symptom severity, includes bronchodilators and inhaled corticosteroids for control of inflammation. Biologic agents targeting inflammatory mediators have been developed for severe persistent asthma.

Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Acutely, sarcoidosis presents with lymphadenopathy, fever, malaise, joint pains, panniculitis on the shins known as erythema nodosum, and occasionally cough and shortness of breath. Chronic pulmonary sarcoidosis presents with an insidious onset of dyspnea, cough, chest pain, and a variety of other symptoms depending on the organ systems involved. Diagnosis often requires a biopsy of the granulomas. Management includes observation, NSAIDs, glucocorticoids, and potentially one of several steroid-sparing agents. Acute sarcoidosis is usually self-limiting with an excellent prognosis, but chronic sarcoidosis can lead to severe pulmonary fibrosis.

Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in individuals over age 40 with a history of more than 40 pack-years of cigarette smoking. Symptoms include progressive dyspnea and chronic cough. Prolonged expiration, wheezing, and/or diminished breath sounds may be noted on physical exam. The diagnosis is confirmed with a pulmonary function test. Management includes smoking cessation, pulmonary rehabilitation, and pharmacotherapy.

Diagnostic modalities such as chest X-rays provide static images of the thoracic cavity, including the lungs and airways. While providing a wealth of anatomical information necessary for the diagnosis of pulmonary disease, chest X-rays do not give much information about the individual's respiratory function. Pulmonary function tests are a group of diagnostic procedures yielding useful, quantifiable information about the rate of the flow of air through the individual's airways, lung capacity, and the efficiency of gas exchange in relation to time. The most commonly utilized tests include spirometry (before and after bronchodilator use), lung volumes, and quantitation of diffusing capacity for carbon monoxide (CO). The tests can be influenced by the individual's effort/fatigue, disease state, or anatomical malformation.

Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. To perform this function, the lungs need to be able to capture as much O2 as possible, a task that is easily achieved owing to their elastic morphology. Each lung is enclosed within the visceral pleura and completely fills 1 of the non-symmetrical pleural cavities, which are situated on the left and right sides of the mediastinum. The lungs encase the bronchial tree and are divided functionally and anatomically into lobes.

Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Acutely, sarcoidosis presents with lymphadenopathy, fever, malaise, joint pains, a panniculitis on the shins known as erythema nodosum, and occasionally cough and shortness of breath. Chronic pulmonary sarcoidosis presents with an insidious onset of dyspnea, cough, chest pain, and a variety of other symptoms depending on the organ systems involved. Diagnosis often requires a biopsy of the granulomas. Management includes observation, NSAIDs, glucocorticoids, and potentially one of several steroid-sparing agents. Acute sarcoidosis is usually self-limiting with an excellent prognosis, but chronic sarcoidosis can lead to severe pulmonary fibrosis.

Lung cancer is the malignant transformation of lung tissue and the leading cause of cancer-related deaths. The majority of cases are associated with long-term smoking. The disease is generally classified histologically as either small cell lung cancer or non-small cell lung cancer. Molecular profiling of the cancer provides further distinction of the tumor's biological behavior, prognosis, and treatment options. Symptoms include cough, dyspnea, weight loss, and chest discomfort. Regional and metastatic spread cause additional symptoms and complications depending on the location and organ(s) affected. Related paraneoplastic syndromes include hypercalcemia, hyponatremia, Lambert-Eaton syndrome, Cushing's syndrome, polydermatomyositis, and dermatomyositis. Definitive diagnosis and staging are made by biopsy, genetic mutation with biomarker testing, and imaging. Management is guided by the cancer stage and associated molecular profile. Lung cancer carries an overall poor prognosis.

Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Diagnosis is confirmed with a pulmonary function test showing a reversible obstructive pattern. Treatment, based on symptom severity, includes bronchodilators and inhaled corticosteroids for control of inflammation. Biologic agents targeting inflammatory mediators have been developed for severe persistent asthma.

Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy.

Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Symptoms include progressive dyspnea and chronic cough. Prolonged expiration, wheezing, and/or diminished breath sounds may be noted on physical exam. The diagnosis is confirmed with a pulmonary function test. Management includes smoking cessation, pulmonary rehabilitation, and pharmacotherapy.