The lung in multi-system diseases

Sickle cell disease

This is an autosomal recessive disease producing abnormal haemoglobin (the iron-containing protein in the red blood cells which gives blood its colour). The red blood cells become distorted, especially in conditions where there blood oxygen is low. Sickle cell disease mainly affects people of African origin. Although it may affect other organs, it is particularly troublesome in the lungs in places where the oxygen level is low. The haemoglobin “sickles”, clotting up small arteries and reducing the oxygen level further. This can occur suddenly, often during an infection, resulting in a severe illness called a “sickling crisis”.

Auto-immune diseases (Connective Tissue Disorders)

Autoimmune diseases are very rare in children. The body appears to react against itself. Inflammation is produced in many organs, including the lungs. The causes are often unknown but the diseases are rare in children. When the inflammation involves the gas-exchanging parts of the lung (alveoli), it often causes scarring (pulmonary fibrosis). This will make the lungs stiff and increases breathlessness.

• Systemic lupus erythematosis; this auto-immune disease results in pulmonary fibrosis and may attack any, or all, of the following organs - skin, lungs, heart, liver, kidney, blood vessels and nervous system. In the lungs, it causes breathlessness. This is due to lung damage produced in various ways, including:
  - inflammation (interstitial pneumonitis, lupus-related pneumonitis)
  - bronchiolitis obliterans (where inflammation and scarring block very small airways)
  - bleeding into the lung
  - weakness of the breathing muscles, particularly the diaphragm
  - thickening and stiffness of the arteries supplying the lung (pulmonary hypertension)
  - fluid around the lungs (pleural effusions)

• Sceroderma; this autoimmune disease involves lung, gullet, kidney and skin. In the lung it may produce pulmonary fibrosis, pulmonary hypertension and reduced function of the diaphragm. All of these will contribute to breathlessness. Aspiration of stomach contents due to problems with the gullet will result in repeated chest infections.

• Dermatomyositis; the main organs affected by this inflammation are skin, muscle and lung. Again it causes pulmonary fibrosis and cysts in the lung. These may burst so that air escapes outside the lung to produce a pneumothorax. Pulmonary hypertension can become severe and the diaphragm may weaken. The main problems are similar to those in scleroderma.