1. Interstitial lung disease (ILD)

Interstitial lung diseases such as NSIP and LIP are related to immune dysregulation and are now seen much less frequently due to the use of ART (50). 

Lymphocytic Interstitial Pneumonitis (LIP) 

This has been described predominantly in children with low CD4 T -cell counts and is characterised by bilateral reticulonodular interstitial opacities in the middle and lower lung zones (41).   Other imaging findings include basal reticulation, ground-glass opacities, ill-defined centrilobular and subpleural nodules, thin-walled cysts, peribronchovascular interstitial thickening, and interlobular septal thickening.  Cysts may result from bronchiolar obstruction by lymphocytic infiltrates with post-obstructive ectasia (48). Diffuse hyperplasia of bronchus-associated lymphoid tissue is seen and the dominant microscopic feature of LIP is a diffuse, polyclonal lymphoid cell infiltrate surrounding airways and expanding the lung interstitium. LIP may be seen in association with autoimmune disorders (48). 

Nonspecific Interstitial Pneumonitis (NSIP) 

This is a histological diagnosis, requiring the exclusion of other causes, and the condition may be part of the “lymphocytic pulmonary syndromes” associated with HIV infection (49). NSIP is characterized by the presence of an interstitial infiltrate of lymphocytes, plasma cells, and macrophages. In severe cases, the infiltrate may extend into alveolar septae (49). The presentation of NSIP is similar to that of pneumocystis pneumonia although it be present at higher CD4 cell counts. Chest radiographs may be normal although typical changes include ground-glass opacities and fibrosis.  The condition may improve without specific therapy and may even be seen as an incidental finding on lung biopsy (49, 50). 

2. Bronchiectasis 

Bronchiectasis is characterised by dilatation of airways, impaired mucociliary clearance and recurrent infection. Bronchiectasis rates have been reported to be increased in both paediatric and adult populations living with HIV (46, 51).In the pre-ART era, a US study reported a 6%prevalence of bronchiectasis in a group of HIV-infected children. Studies from Africa report higher rates of bronchiectasis in children (52). Multiple pulmonary insults, include infection and immunodeficiency, can result in bronchiectasis.  Such factors are associated with HIV infection however, some data suggest that HIV may predispose to bronchiectasis independently of infection, likely due to defects in innate immunity and accompanying airway neutrophilic inflammation (52). Bronchiectasis in adolescents may be seen as a late complication of LIP (46). 

3. Cryptogenic Organising Pneumonia and Hypersensitivity Pneumonitis

Cryptogenic Organising Pneumonia is a pattern of lung tissue repair after injury. The condition may be idiopathic or a response to many different forms of lung injury including viral infections such as HIV.  The condition may manifest with cough and dyspnoea, often as a syndrome of failure to improve after a previous infectious illness.  The radiological appearances may be diverse, but often bilateral patchy or diffuse changes are seen in the presence of normal lung volumes(53). The condition may be seen in association with Pneumocystis jiroveci pneumonia and may be a manifestation of IRIS (50).  

Hypersensitivity pneumonitis results from a disordered CD8+ inflammatory response to an extrinsic allergen. The condition was uncommonly associated with HIV infection, but with the advent of HAART, it has been described in HIV-infected individuals exposed to several agents, including efavirenz, dapsone and bleomycin (49, 50). It may also be observed after the initiation of HAART (54). 

4. Pulmonary  Arterial Hypertension (PAH) 

PAH appears to be more common in individuals living with HIV (50). Prevalence rates in persons living with HIV vary from 0.46% to 10% (55,56). Symptoms of this disorder include progressive dyspnoea, chest pain and syncope. Examination shows features of pulmonary hypertension and chest radiology shows cardiomegaly and enlargement of the pulmonary arteries (50). If the diagnosis is suspected, specialist referral and investigation is warranted. Outcomes in those with PAH and HIV appear to be worse than in those without HIV. One cohort reported a survival rate of 72% at 3 years, and cardiac function and CD4 counts both predictive of mortality (57).