Abstract Body (Do not enter title and authors here): Case Description:
A 69-year-old female with rheumatoid arthritis (RA) on methotrexate, rituximab, and prednisone presented with pleuritic chest pain, fever and cough. Vitals were stable. EKG showed diffuse ST elevation with PR depression, suggestive of pericarditis. TTE showed no pericardial effusion. She was discharged on colchicine.
She returned 6 days later with worsening chest pain, dyspnea, and orthopnea. Vitals: BP 96/63 mm Hg, pulse 88 bpm. Exam revealed increased work of breathing, muffled heart sounds, no murmurs, no JVD. EKG showed low-voltage QRS with electrical alternans. CXR revealed bilateral opacities and cardiomegaly. CRP was 18.6 mg/dL, ESR 44 mm/hr, and Mycoplasma IgM was positive.
Repeat TTE showed a moderate pericardial effusion (2 cm) near the RV free wall. There was no RV diastolic collapse, but >25% MV E-wave respiratory variation was seen.
Cardiology was consulted and she underwent ultrasound-guided pericardiocentesis, draining 450 cc serosanguinous fluid. Fluid analysis showed exudative effusion (WBC 24,194, protein 5.5 g/dL, LDH 1,642). Rheumatology was consulted who suspected immunosuppression-related M. pneumoniae pericarditis. Immunosuppressants were held. She was treated with doxycycline, colchicine, and ibuprofen. With normal follow-up TTEs, pericardial drain was removed. She was discharged in stable condition after 7 days.

Discussion:
This case demonstrates a cardiac tamponade due to rapid accumulation of moderate pericardial fluid from immunosuppresion-induced Mycoplasma pneumoniae pericarditis. Tamponade may occur with moderate effusions with rapid accumulation or in low-pressure like diuretic-use or dry tamponade post-procedure.
Pericardial effusion aetiologies include idiopathic, malignancy, infection, uremia, connective tissue disease, surgery. Viral pericarditis is most common infection, often due to Coxsackievirus or Influenza. Bacterial causes like S. pneumoniae or S. aureus may lead to purulent effusion. M. pneumoniae typically mimics viral pericarditis and may be overlooked. Without Mycoplasma IgM testing, diagnosis and treatment may be delayed.
ESC’s 2014 guidance for triaging cardiac tamponade patients recommends urgent pericardiocentesis for scores >6; our patient’s score was 11.5, supporting intervention.
This case emphasizes the importance of considering atypical pathogens like M. pneumoniae in immunocompromised hosts with pericarditis and using clinical scoring and imaging for timely intervention.