Pneumomediastinum in an HIV-infected patient with cytomegalovirus pneumonitis

INTRODUCTION

A pneumomediastinum refers to the presence of air in the mediastinum and it is usually a benign condition, occurring spontaneously in healthy young adults. ^1,2 It can also occur secondary to trauma, surgery or infection. In HIV-infected patients it has been described as a potentially life-threatening complication of pneumocystis pneumonia (PCP). ^2,3 While cytomegalovirus (CMV) infection has been previously linked with pneumomediastinum, this has not been reported in the context of HIV infection. ⁴ We describe the development of a pneumomediastinum in an HIV-infected patient with CMV pneumonitis, initially diagnosed as pneumocystis pneumonia.

CASE PRESENTATION

A 27-year-old African woman presented to a hospital in Harare, Zimbabwe, with a month's history of a non-productive cough, increasing shortness of breath, night sweats and fevers. A chest radiograph (CXR) performed two weeks previously to investigate possible tuberculosis had been unremarkable and three sputum smear examinations were negative for acid-fast bacilli. On examination she was in marked respiratory distress, tachypnoeic at 50 breaths per minute, cyanosed and febrile. She had a herpes zoster scar over the right T6 dermatome. Examination of the other systems was unremarkable. A CXR showed diffuse reticulo-nodular shadowing in the lower and mid-zones (Figure 1a).

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Figure 1

(a) The initial chest X-ray showing diffuse reticulo-nodular shadowing in the middle and lower zones. (b) Follow-up chest X-ray. Note the subcutaneous emphysema (white arrow) and air in the mediastinal space (black arrows)

A full blood count showed white cell count 6.9 × 10³/μL (neutrophils 79%, lymphocytes 14%, monocytes 5%, eosinophils 2% and basophils 0.1%), haemoglobin 11 g/dL, platelets 310 × 10³/μL. An HIV-1 antibody test was positive and her CD4 count was 65 cells/mm³. The clinical picture was suggestive of PCP and she was commenced on empiric therapy with high-dose oral co-trimoxazole 1920 mg thrice daily, prednisolone 60 mg once daily and high flow of oxygen. There was slow but gradual improvement over the first two weeks, with resolution of fever and cyanosis, but she remained breathless at rest.

Sixteen days after admission her condition deteriorated, with development of severe respiratory distress and paroxysms of coughing. On examination she had developed diffuse neck swelling, with palpable crepitus over the neck and anterior chest wall. There was no clinical evidence of a pneumothorax. A CXR (Figure 1b) showed a pneumomediastinum with subcutaneous emphysema. She was managed conservatively with oxygen and analgesia but she developed a right-sided pneumothorax five days later. At this point, a chest drain was inserted and a lung biopsy was performed.

The lung histology showed the typical ‘owl-eye’ inclusions of CMV infection, marked interstitial thickening of the lung parenchyma and proliferation of type II pneumocytes. A diagnosis of CMV pneumonitis was made and she was commenced on oral ganciclovir 1 g thrice daily. However, a second pneumothorax developed on the left side and she refused any further invasive intervention and died six weeks after hospital admission.

DISCUSSION

CMV pneumonitis generally occurs in immunocompromised hosts, including organ transplant recipients and patients on chemotherapy or immunosuppressive therapy for auto-immune diseases. ⁵ Invasive CMV infection is well recognized as an AIDS-defining condition, occurring at extremely low CD4 counts. ⁶ Despite the severe HIV epidemic in sub-Saharan Africa, with many patients presenting with advanced immunosuppression, CMV is rare in adults and not considered routinely in the differential diagnosis in practice. ⁷ This is in contrast to African children, where CMV pneumonitis is common. ⁸

The clinical presentation is similar to that of PCP, being dominated by progressive dyspnoea and hypoxia. ^5,9 The radiological features are also similar, ranging from normal to ground-glass opacities, consolidation, reticular opacities, nodular opacities, and even cysts, cavities and lymphadenopathy on CXR or CT scan. ^9,10 Thus, these infections are difficult to differentiate without histological or microbiological investigations, which may not be available in resource-limited settings. In Zimbabwe, the diagnosis of PCP is usually based on clinical and radiological grounds, while CMV infection is inferred from pathognomonic histological appearances. Culture or polymerase chain reaction methods for the diagnosis of CMV infection are generally not available.

In the present case, the initial diagnosis of PCP was made clinically, due to limited diagnostic facilities. However, several studies suggest that PCP is uncommon in African adults. ¹¹ The use of primary prophylaxis with co-trimoxazole should further reduce the risk. ¹² This makes it imperative that alternative diagnoses or mixed infections be considered when one is confronted with a clinical picture suggestive of PCP. It should be emphasized that CMV can also be present in the lungs as a ‘bystander’ infectious agent, usually demonstrated in bronco-alveolar lavage fluid. ¹³ However, our patient presented with possible PCP, but histologically evident CMV pneumonitis, with consistent clinical features. To the best of our knowledge, this is the first report of pneumomediastinum associated with CMV pneumonitis in the context of HIV infection. This highlights the need for vigilance for a broad range of infections and their complications in HIV-infected patients with advanced immunodeficiency.