5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease

1. Bronchiectasis

Bronchiectasis is permanent, abnormal dilation of the bronchi resulting from a self-perpetuating cycle of infection, inflammation and airway wall destruction. It is listed as its own blueprint subsection.

Presentation: chronic productive cough with large-volume purulent sputum, recurrent exacerbations, hemoptysis (occasionally massive from hypertrophied bronchial arteries), and crackles with occasional wheeze.

Diagnosis is radiologic. High-resolution CT shows bronchial dilation exceeding the diameter of the accompanying pulmonary artery (the signet ring sign), lack of normal distal tapering, and airway visibility within 1 cm of the pleura. Tram-track opacities may be visible on plain radiographs.

Finding the cause is the exam task

Bronchiectasis is a pattern of injury, not a diagnosis. Every case requires an etiologic workup:

Two patterns worth memorizing. Upper-lobe predominant bronchiectasis suggests cystic fibrosis or allergic bronchopulmonary aspergillosis. Right middle lobe and lingular bronchiectasis with nodules in an older thin woman is the Lady Windermere syndrome of Mycobacterium avium complex infection.

Management is airway clearance (chest physiotherapy, hypertonic saline), treatment of exacerbations with antibiotics directed by prior sputum cultures, chronic macrolide therapy for frequent exacerbators after excluding non-tuberculous mycobacteria, and treatment of the underlying cause. Inhaled corticosteroids are not routine unless there is coexisting asthma or COPD.

2. Allergic Bronchopulmonary Aspergillosis

A hypersensitivity reaction to Aspergillus fumigatus colonizing the airway, occurring almost exclusively in asthma or cystic fibrosis. Suspect it in an asthmatic with recurrent infiltrates, brownish mucus plugs and worsening control despite adherence.

Diagnostic features: markedly elevated total IgE (typically above 1,000 IU/mL), positive Aspergillus skin test or specific IgE, precipitating antibodies, eosinophilia, and central (proximal) bronchiectasis — the reverse of most causes, which are distal.

Treatment is systemic corticosteroids with itraconazole as a steroid-sparing agent. This is one of the few pulmonary conditions in which a fungal organism is treated primarily with immunosuppression rather than antifungals alone.

3. Cystic Fibrosis in Adults

Autosomal recessive CFTR dysfunction. Because survival now extends well into adulthood and milder genotypes present late, cystic fibrosis is a real adult internal medicine diagnosis and is enumerated under both Pulmonary Disease and Gastroenterology.

Adult presentations to recognize:

• Bronchiectasis with chronic Pseudomonas aeruginosa or Staphylococcus aureus colonization
• Pancreatic exocrine insufficiency with steatorrhea and fat-soluble vitamin deficiency
• Cystic fibrosis-related diabetes
• Chronic rhinosinusitis with nasal polyps
• Male infertility from congenital bilateral absence of the vas deferens — often the sole manifestation of a mild genotype
• Distal intestinal obstruction syndrome; biliary cirrhosis

Diagnosis: sweat chloride testing is first line, supplemented by CFTR genotyping. Adults with mild variants may have intermediate sweat chloride values.

CFTR modulator therapy has transformed outcomes for patients with responsive genotypes and is now the cornerstone of care alongside airway clearance, inhaled antibiotics and pancreatic enzyme replacement.

4. Alpha-1 Antitrypsin Deficiency

Listed under congenital lung disease. Loss of antiprotease protection permits neutrophil elastase to destroy alveolar walls.

The distinguishing features versus ordinary smoking-related COPD:

Current guidance recommends testing every patient diagnosed with COPD at least once, using a serum alpha-1 antitrypsin level with phenotyping or genotyping if low. Smoking cessation is the single most important intervention, because smoking accelerates decline dramatically in these patients. Intravenous augmentation therapy is available for those with severe deficiency and established emphysema; it does not treat the liver disease.

5. Restrictive Lung Disease Other Than Interstitial and Pleural Disease

A named blueprint subsection listing pulmonary complications of obesity, chest wall disorders, neuromuscular disorders and undifferentiated restrictive disease. These are extrapulmonary causes of restriction — the lung parenchyma itself is normal.

Reading the pulmonary function pattern

The diffusing capacity is the discriminator. Parenchymal disease damages the alveolar-capillary membrane and lowers DLCO. Extrapulmonary restriction merely compresses a normal lung, so DLCO corrected for alveolar volume is preserved or even elevated. A patient with reduced lung volumes and a normal DLCO/VA has a chest wall, neuromuscular or obesity problem — not interstitial lung disease.

Neuromuscular weakness

The highest-yield bedside test is spirometry performed supine as well as upright. Diaphragmatic weakness causes the forced vital capacity to fall by more than 10 to 20% on lying flat, because abdominal contents are no longer opposed by gravity. Maximal inspiratory and expiratory pressures quantify the deficit.

This matters clinically in amyotrophic lateral sclerosis, Guillain-Barre syndrome, myasthenia gravis and muscular dystrophy. In acute neuromuscular respiratory failure, arterial blood gases are a late and misleading indicator — carbon dioxide retention appears only after substantial reserve is exhausted. Serial vital capacity and negative inspiratory force identify the patient who needs intubation before decompensation.

Obesity and the chest wall

Obesity reduces functional residual capacity and expiratory reserve volume with a relatively preserved total lung capacity until it is severe. Kyphoscoliosis produces restriction proportional to the Cobb angle and can cause chronic hypercapnia and cor pulmonale. Ankylosing spondylitis fuses the costovertebral joints, producing chest wall restriction with a characteristically preserved or increased functional residual capacity because the chest is fixed in inspiration.