Case Studies

 Case 7.2 Pneumocystis pneumonia complicating immunosuppressive therapy

A 35-year-old man with Wegener's granulomatosis (WG) was admitted to hospital with a 2-week history of fever and shortness of breath. The diagnosis of WG had been made 18 months earlier when he presented with haemoptysis and glomerulonephritis. Disease remission was achieved with aggressive immunosuppressive therapy using a combination of pulse methylprednisolone and cyclophosphamide, enabling him to be maintained on his current tapering dose of steroids and azathioprine. The results of investigations on his current hospital admission were as follows:

• Chest X-ray: diffuse bilateral shadowing.
  
• Serum C-reactive protein (CRP): 80mg/l (NR <10).
• Antineutrophil antibody (cytoplasmic pattern): weakly positive at a titre of 1:40 (>1:640 at disease diagnosis).
  
• Serum creatinine: 102µmol/l (NR 50-140).
• Urea: 4.5mmol/l (NR 2.5-7.1).
• Urine microscopy: clear.

The differential diagnosis was between active WG and infection complicating immunosuppressive therapy. It was crucial to distinguish between infection and active vasculitis in this situation, since an increase in immunosuppressive therapy in the face of sepsis could be potentially fatal. Further investigations, including bronchoalveolar lavage, revealed the presence of Pneumocystis carinii, a recognized lung pathogen in patients on long-term immunosuppressive therapy. He made a full clinical and radiological recovery following 2 weeks of co-trimoxazole therapy and was discharged home on his usual dose of maintenance immunosuppression.