Nataša Moser

Background: Nearly 10% of all community-acquired pneumonias are caused by Chlamydia pneumoniae. This is a Gram-negative intracellular coccus that poses a significant challenge for routine diagnostics due to its poor growth in tissue culture and non-specific clinical presentations. Case Report: This study presents the case of a 61-year-old man whose initial disease manifestation included a non-specific upper respiratory tract infection and reactive pericarditis. A diagnostic work-up of the etiology of pericarditis, with stepwise exclusion of other causative agents, led to confirmation of a possible chronic, recurrent C. pneumoniae infection, with good clinical and laboratory responses to azithromycin across multiple hospitalizations. However, upon initiation of prolonged doxycycline therapy, the disease course was complicated by the development of Guillain–Barré syndrome. With appropriate treatment, the neurological deficit regressed, with near-complete resolution of the syndrome’s clinical picture. Discussion and Conclusions: The development of reactive pericarditis and the patient’s neurological symptoms stemmed from an immune response to bacterial antigens that resemble antigens of the central nervous system and the pericardium. Prolonged doxycycline therapy, together with symptomatic management of the neurological condition and concomitant pericarditis, represents good clinical practice and is one potential management approach for patients with similar presentations.