Cystic Fibrosis – Top USMLE Diseases

Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Upper airway obstruction (UAO) and central airway obstruction (CAO) refers to a mechanical blockage of the large airways and are potentially life-threatening events, which need to be recognized and managed promptly.

Burkholderia species are gram-negative bacilli with 2 clinically relevant pathogens: B. pseudomallei (causing melioidosis) and B. cepacia complex (causing opportunistic infections). Melioidosis is commonly seen in Asia and Australia. Infection is transmitted by contact with contaminated soil or water (via skin wounds). The disease affects multiple systems, and can present with pneumonia, encephalomyelitis, and skin abscesses. Diagnosis is by culture of specimen (depending on the organ involved). Treatment requires an initial intensive antibiotic therapy followed by prolonged eradication therapy. Burkholderia cepacia complex (BCC) generally affects immunocompromised individuals such as those with cystic fibrosis (CF). It can be transmitted from person to person or through contaminated devices. While BCC is a rare infection, it is important to diagnose, as BCC is multi-drug resistant and infection is a relative contraindication to lung transplantation.

Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Only 5%–15% of patients with hemoptysis have life-threatening bleeding. However, hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. The most common causes of hemoptysis include bronchiectasis, lung cancer, tuberculosis, and aspergillosis. Diagnosis involves chest imaging and bronchoscopy. In cases of life-threatening bleeding, treatment is initially directed at stabilizing the patient and, if bleeding is ongoing, hemostasis can often be achieved with minimally invasive techniques (e.g., arterial embolization).

Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Most cases are idiopathic, though infections, bronchial obstruction, congenital disorders, and systemic conditions can contribute. Patients present with slowly progressive symptoms of cough and sputum production. The diagnosis is made from characteristic radiographic findings, such as bronchial wall thickening and luminal dilatation. Management focuses on improving clearance of mucus, relieving airway obstruction, treating infection, and managing the underlying etiology. Management can include chest physiotherapy, bronchodilators, and antibiotics.

Cystic fibrosis is an autosomal recessive disorder caused by mutations in the gene CFTR. The mutations lead to dysfunction of chloride channels, which results in hyperviscous mucus and the accumulation of secretions. Common presentations include chronic respiratory infections, failure to thrive, and pancreatic insufficiency. The gold standard for diagnosis is the sweat chloride test, which can be complemented by genetic testing. Cystic fibrosis ultimately leads to chronic inflammation and multisystem organ failure. Management includes CFTR modulator therapy and system-specific strategies for supportive care. Prognosis varies depending on treatment and complications. With optimal medical care, patients can live into their mid-40s.