Cytomegalovirus pneumonia is an inflammation of the lung tissue caused by primary or secondary infection by the cytomegalovirus, which belongs to the Herpesviridae group of viruses. It mostly affects immunocompromised individuals.
Cytomegalovirus (CMV) pneumonia can occur regardless of host immune status, however, the infection is latent in immunocompetent individuals. Reactivation of the virus is possible, and this leads to secondary infection.
In the context of a normally functioning immune system, infection is largely asymptomatic and full blown pneumonia is rare, even if infiltrates are visible radiologically. Fever, lymphadenopathy and flu-like symptoms, in what is termed CMV mononucleosis, with or without the presence of a cough, is the most frequently described clinical presentation. In the event that severe pneumonia is contracted, full recovery following initiation of antiviral treatment is typical.
In practice, most documented cases of cytomegalovirus pneumonia are confined to immunosuppressed individuals, and the disease is often severe and fatal. This includes those who have undergone chemotherapy, radiotherapy, long-term steroid therapy, organ and bone marrow transplant recipients and those suffering from acquired immunodeficiency syndrome (AIDS). The latter are at the highest risk when serum concentrations of T helper cells fall below 50 cells per cubic millimeter. Among those who receive organ transplants, the probability of CMV pneumonia differs; for instance those who receive cells or organs originating from another donor have up to a 30% risk, whereas those receiving their own harvested cells have a much lower risk (1%- 6%) [1]. Furthermore, bone marrow transplant recipients are the most susceptible to disease, with untreated case fatality rates of over 80%, and 15-75% with appropriate treatment [1]. Symptoms experienced include
Symptoms of CMV pneumonia include cough, fever, night sweats, respiratory distress, hypoxia, myalgia, arthralgia, and fatigue. Radiological evidence of disease can sometimes precede outward signs of infection. The infection may affect other organ systems simultaneously, thus provoking a wider symptom profile. As it is a life-threatening illness, immunosuppressed patients are habitually initiated on CMV prophylaxis [2] [3] [4].
Importantly, neonates can also suffer from cytomegalovirus pneumonia when they acquire the infection from infected mothers through the placenta, birth canal, or during and breastfeeding.
The diagnosis of CMV pneumonia combines both clinical observation and medical imaging. Chest X-ray and computerized tomography (CT) scan are the relevant imaging techniques. They may show ground glass or patchy opacities across both lung fields [5] [6]. Despite this, possible X-ray and CT findings are variable.
Laboratory tests involve collecting tissue samples from the blood, urine or alveoli through bronchoalveolar lavage. These samples are used for serology through the means of immunological assays, viral culture, and DNA polymerase chain reaction (PCR). Caution should be exercised when interpreting results, as they can be misleading. Histopathologic diagnosis, for which a lung biopsy is needed, is more accurate but may prove hazardous for bedridden patients [7].