Asthma

Asthma is a relatively common condition that is characterised by at least partially reversible inflammation of the airways and reversible airway obstruction due to airway hyper-reactivity. It can be acute, subacute or chronic.

Pathology

Distribution

It mainly involves the medium sized and small bronchi ⁶.

Histology

Asthma is histologically characterised by the presence of chronic inflammation of the airways. The bronchi are thickened by a combination of oedema, bronchial wall smooth muscle hyperplasia and an increase in the size of the mucous glands associated with the airways. Crystalline granules called Charcot-Leyden crystals form in eosinophils. Spiral-shaped mucous plugs (Curschmann's spirals) are seen in the sputum ¹⁵. 

Associations

• Samter syndrome

Radiographic features

ChestPlain radiograph

Plain filmschest radiographs can be normal in upto 75% of patients with asthma.

Reported features with asthma include:

• pulmonary hyperinflation
• bronchial wall thickening: peribronchial cuffing (non specific finding but may be present in ~48% of cases with asthma ¹)
• pulmonary oedema (rare): pulmonary oedema due to asthma (usually occurs with acute asthma)

CT Chest/HRCT chest

CT is usually use to detect the presence of complicated associated conditions such as allergic bronchopulmonary aspergillosis and not to directly diagnose asthma.

Reported HRCT features of asthma are non specific as individual features, they include ²:

• bronchial wall thickening ^2-3
• expiratory air trapping
• inspiratory decreased lung attenuation
• small centrilobular opacifities ^6,8
• bronchial luminal narrowing: reduced bronchoarterial-diameter ratio ⁷
• subsegmental bronchiectasis: may be present in ~28-62% of asthmatics ^8,12

Complications

There are several conditions that can complicate asthma, they include ^1,6:

• atelectasis
• pneumonia
• mucoid impaction of the airways
• eosinophilic lung disease
  • allergic bronchopulmonary aspergillosis
  • bronchocentric granulomatosis
  • Churg-Strauss syndrome

Asthma is a huge topic and there are entire books written on it. Feel free to upgrade this article