Is mycoplasma infection a risk factor for worsening pulmonary embolism (PE)?

Is Mycoplasma a Risk Factor for Worsening Pulmonary Embolism?

Mycoplasma infection is not recognized as a risk factor for pulmonary embolism in major international guidelines, though emerging case reports suggest it may trigger PE in rare circumstances, particularly in children with severe refractory pneumonia. The 2019 ESC/ERS Guidelines do not list mycoplasma among the established risk factors for venous thromboembolism or PE 1.

Guideline-Established Risk Factors for PE

The authoritative risk stratification from the European Society of Cardiology identifies three tiers of PE risk factors, none of which include mycoplasma infection 1:

Strong risk factors (OR >10):

• Lower limb fractures
• Hip or knee replacement
• Major trauma
• Myocardial infarction within 3 months
• Previous VTE
• Spinal cord injury 1

Moderate risk factors (OR 2-9):

• Infection (specifically pneumonia, urinary tract infection, and HIV) - notably, this refers to bacterial pneumonia in general, not mycoplasma specifically 1
• Cancer (highest risk in metastatic disease)
• Chemotherapy
• Central venous catheters
• Autoimmune diseases 1

Weak risk factors (OR <2):

• Bed rest >3 days
• Diabetes mellitus
• Arterial hypertension
• Increasing age
• Obesity 1

Emerging Evidence on Mycoplasma and PE

While guidelines do not recognize mycoplasma as a specific PE risk factor, recent case reports and small case series suggest a potential association:

Pediatric cases show the strongest signal:

• A Chinese pediatric series of 7 cases found that children with critical Mycoplasma pneumoniae pneumonia (MPP) had elevated PE risk, with 2 deaths among 5 surgical cases 2
• A retrospective study of 9 children with MPP-associated PE found all had refractory MPP, with median 14 days from infection to PE diagnosis 3
• Most pediatric cases presented with transient autoantibody positivity (lupus anticoagulant, anticardiolipin antibodies) and abnormal coagulation 3

Adult cases are extremely rare:

• Only one case report describes acute saddle PE in an adult with mycoplasma pneumonia, representing the first documented live adult case 4

Clinical Implications and Pitfalls

The key distinction is that mycoplasma may trigger PE rather than worsen existing PE. The mechanism appears to involve:

• Transient hypercoagulability with autoantibody production 3
• Inflammatory cascade activation 2
• Coagulation factor abnormalities (elevated factor VIII, reduced protein C/S) 3

Common pitfalls to avoid:

• Do not confuse "infection as a moderate risk factor" in guidelines with mycoplasma-specific risk - the guideline evidence refers to bacterial pneumonia, UTI, and HIV 1
• Mycoplasma-associated PE occurs almost exclusively in refractory or severe cases, not typical mycoplasma infections 2, 3
• Consider PE in pediatric patients with refractory MPP who deteriorate despite appropriate antibiotics, particularly if D-dimer is markedly elevated 2, 5, 3

Practical approach when mycoplasma pneumonia is present:

• Maintain high suspicion for PE in children with refractory MPP who develop dyspnea, chest pain, or clinical deterioration 2, 5, 3
• Check D-dimer, anticardiolipin antibodies, and lupus anticoagulant if PE is suspected 3
• Proceed to CT pulmonary angiography if clinical suspicion is high 2, 5, 3
• Early anticoagulation with low-molecular-weight heparin followed by rivaroxaban has shown good outcomes in pediatric cases 3

The evidence quality is low - consisting only of case reports and small retrospective series, insufficient to establish mycoplasma as a recognized risk factor in clinical practice 4, 2, 5, 3. The 2019 ESC/ERS Guidelines remain the authoritative source for PE risk stratification, and they do not include mycoplasma 1.