Bronchial Disease and Pulmonary Hypertension

Comprehensive vocabulary flashcards covering the etiology, pathophysiology, and morphological classifications of bronchiectasis, bronchiolitis subtypes, and the World Health Organization classifications and mechanisms of pulmonary hypertension.

Bronchiectasis

A chronic pulmonary condition defined by irreversible dilation of the airways caused by destruction of the airway walls.

Cystic fibrosis bronchiectasis

A genetic form of bronchiectasis associated with cystic fibrosis, occurring in approximately $1:2000\text{--}3500$ live births in North America and Europe.

Ciliary dynein arm deficiency

An ultrastructural defect in which the dynein arms of cilia are absent in the lower airways and nasal mucosa, resulting in impaired mucociliary clearance, recurrent infections, and bronchiectasis.

Cylindrical (tubular) bronchiectasis

A morphological pattern of bronchiectasis characterized by affected airways that appear uniformly widened.

Varicose bronchiectasis

A morphological pattern of bronchiectasis characterized by irregularly widened and deformed airway lumens.

Saccular (cystic) bronchiectasis

A severe morphological pattern of bronchiectasis characterized by balloon-like or sac-like dilation of the peripheral airways.

Vicious cycle hypothesis

A pathophysiological model of bronchiectasis stating that an initial event impairs mucociliary clearance, leading to microbial colonization, epithelial injury, and chronic inflammation, which causes further airway wall dilation and damage.

Neutrophil elastase

A proteolytic enzyme released by airway neutrophils that degrades bacteria but can also destroy host structural proteins (elastin, fibronectin, collagen, and $\alpha_1\text{-antitrypsin}$), impair phagocytosis, cause ciliotoxicity, and activate matrix metalloproteinases.

Matrix metalloproteinases (MMPs)

Proteases activated by neutrophil elastase that degrade the airway extracellular matrix, playing a critical role in pathological airway remodeling.

Bronchioles

Conducting airways beginning at the 16th generation with an internal diameter of $\le 1\,\text{mm}$, lacking cartilage, possessing a thin muscular layer, and lined by ciliated columnar cells, secretory columnar cells, Clara cells, and few goblet cells.

Acute bronchiolitis

Acute bronchiolar inflammation characterized by a dense granulocytic and/or lymphocytic infiltrate within the epithelium, accompanied by degenerative and reactive changes without metaplasia or hyperplasia.

Eosinophilic (asthmatic) bronchiolitis

A form of acute bronchiolitis presenting with a mixed wall infiltrate of eosinophils, mast cells/basophils, plasma cells, and lymphocytes, luminal mucus plugs, thickening or hyalinization of the basal lamina, and shedding of Clara and goblet cells.

Pseudomembranous bronchiolitis

A necrotizing form of acute bronchiolitis wherein necrotic epithelial debris mixes with fibrin leaking from capillaries to form a pseudomembrane over the surface of the bronchiole without disrupting the basal lamina.

Granulomatous bronchiolitis

A form of bronchiolitis characterized by granuloma formation; classic granulomas occur with or without necrosis in sarcoidosis, with necrosis in tuberculosis, and as histiocytic lesions in occupational dust diseases (silicosis, coal workers' pneumoconiosis, and asbestosis).

Chronic bronchiolitis

Prolonged bronchiolar inflammation characterized by a lympho-plasmocytic wall infiltrate, conversion of ciliated cells to goblet cells, goblet cell hyperplasia, and smooth muscle hyperplasia or fibrotic replacement.

Bronchiolitis obliterans

A distinct form of bronchiolitis marked by focal epithelial and submucosal tissue necrosis organized by polyp-like inflammatory granulation tissue that protrudes into the lumen, potentially causing complete luminal obliteration.

Constrictive bronchiolitis

A distinct form of bronchiolitis characterized by a lympho-plasmocytic wall infiltrate with early smooth muscle hypertrophy, followed in late stages by muscle atrophy and fibrous tissue replacement that constricts the lumen.

Pulmonary hypertension

A hemodynamic state characterized by an elevated pulmonary arterial pressure defined as $>25\,\text{mmHg}$ at rest or $>30\,\text{mmHg}$ during exercise.

Cor pulmonale

Right ventricular hypertrophy that develops secondary to pulmonary hypertension caused specifically by respiratory disorders of the airways, chest wall, lung parenchyma, or respiratory muscles.

WHO Group 1 Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) consisting of idiopathic, familial, or drug/toxin-induced etiologies, characterized pathologically by intimal and medial wall thickening; overall prevalence is 15 cases per million (idiopathic: 6 cases per million).

WHO Group 2 Pulmonary Hypertension

Pulmonary hypertension caused by left heart disease (such as mitral stenosis or chronic left ventricular failure), which elevates downstream pressure in the left heart and creates back pressure into pulmonary veins, capillaries, and arteries; affects 3 to 4 million people in the US.

WHO Group 3 Pulmonary Hypertension

Pulmonary hypertension associated with underlying chronic lung diseases (such as COPD and interstitial lung disease) and/or alveolar hypoxemia-mediated vasoconstriction.

WHO Group 4 Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) resulting from vascular obstruction due to chronic thrombotic or embolic disease, occurring in $0.5\text{--}2\%$ (up to $3.8\%$) of acute pulmonary embolism survivors.

WHO Group 5 Pulmonary Hypertension

Pulmonary hypertension resulting from miscellaneous, multifactorial systemic conditions that do not fit into the other four defined categories.