Round pneumonia is an inflammatory illness of the lung parenchyma (usually of infectious origin) presented as spherical or oval-shaped consolidation in chest radiography (CR). This well-known clinical-radiological syndrome is generally thought to be a disease of children, being reported rarely in adults1,2. We report two patients with murine typhus (Rickettsia typhi) with a clinical-radiological picture of round pneumonia.
Patient 1: A 58-year-old male who owned cats was admitted to the hospital because of fever, chills, oppressive headache and diffuse abdominal pain in the last four days. Physical exam only revealed moderate tenderness to abdominal palpation. Laboratory tests revealed liver enzymes mildly elevated and thrombocypenia. CR and thoracic computed tomography (CT) showed a nodule of 2cm in upper right lobe with adjacent pneumonitis (Fig. 1a). A broncoscopy was performed but cytological and microbiologic analyses were negative, as well as transbronchial biopsy. Doxycycline was administrated, with remission of fever within 48hours and clinical improvement. Serologic tests for R. typhi were positive (IgM 1/40960 and Ig G 1/320). Thoracic CT obtained fourteen days after onset revealed resolution of nodular image (Fig. 1b).
Patient 2: A 20-year-old male in contact with a dog presented with a 6-day history of fever up to 39.5°C, dry cough, arthralgias, myalgias, headache, sweating and vomiting. He showed a macular rash on the trunk and upper limbs without itching. Results of tests revealed aspartate transaminase slightly elevated, mild thrombocypenia, proteinuria and microhematuria. CR displayed a nodular lesion in middle lobe. Doxycycline was prescribed and patient's condition improved within 72hours, disappearing fever and the remainder of symptoms. Serologic analysis for R. typhi was positive (IgM 1/10.240 and Ig G 1/5120). A CR obtained 14 days after diagnosis was normal.
Round pneumonia is more common in children under 5 years being the lower lobes more commonly affected region. The prevalence in this age group and pulmonary localization is due to anatomical features3. In children, the main agents of round pneumonia are the same as those involved in other radiological forms of pneumonia. In adults, the number of cases is lower and probably their pathogenic mechanisms are differents. In addition, the microorganisms involved are less known and possibly geographical differences exist. Anton and colleagues have described the important role of Coxiella burnetii infection4 and to a lesser extent other atypical pathogens (Legionella pneumophila)5 as causative agents of round pneumonia in Spain. This statement has also been observed in other European countries where Q fever is common6.
In recent years, our group has described in the Canaries the existence of a significant number of cases of murine typhus7. This disease is manifested by high fever, severe headache, musculoskeletal pain, and occasionally rash. Although the classic form of transmission of R. typhi is the bite of fleas, inhalation of contaminated faeces also appears to play an important role. Respiratory involvement is relatively common in this disease8. However, radiographic changes occur only around 6% (interstitial pneumonitis, pleuro-pericarditis with pulmonary thromboembolism and alveolar infiltrates with or without pleural effusion)8. After a comprehensive review we have only found one case of round pneumonia caused by R. typhi9.
We believe that the description of these cases has a dual interest. On the one hand, we should perform a serological survey, which could prevent unnecessary invasive procedures, in any patient with fever and nodular images in areas where R. typhi infection is high. On the other hand, we should include doxycycline in the empirical treatment of round pneumonia in adults, pending microbiological results and depending on the geographic area.
