Haemophilus parainfluenzae endocarditis presenting with symp
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With a varied and often insidious clinical course, infective endocarditis (IE) can be difficult to diagnose but incidence is increasing globally, even in low-risk individuals.

A young man presented early in the UK’s second COVID-19 pandemic surge with a twelve-day history of fever, dry cough, breathlessness, myalgia and loss of smell and taste. His chest X-ray showed bilateral ground-glass opacities. He was treated for COVID-19 pneumonitis but covered for bacterial infection with antibiotics. He developed shock and respiratory failure, requiring vasopressors and continuous positive airway pressure. He improved but experienced transient visual disturbances and headache.

Nasopharyngeal swabs and antibody tests for COVID-19 were negative. Blood cultures grew Haemophilus parainfluenzae. A new murmur prompted an echocardiogram. This confirmed a large, mobile mitral valve vegetation. An MRI of the brain showed bilateral embolic infarcts. He underwent urgent mitral valve repair and made an excellent recovery.

Whether COVID-19 caused his presenting symptoms or facilitated the bacteraemia remains unclear. It seems more likely that infective endocarditis masqueraded as COVID-19. Clinicians should be aware of how context of the pandemic can bias diagnostic reasoning.

Learning points
- Infective endocarditis is a rare but important differential diagnosis in patients with infection and signs of reduced cardiac output or cardiogenic shock.

- Neurological symptoms in the context of infection can suggest an embolic process.

- Haemophilus parainfluenzae is the most common HACEK organism to cause endocarditis and can form large mitral valve vegetations.

- H. parainfluenzae can act in an aggressive manner to cause shock in young, healthy people.

- Clinicians should be astute to diagnostic framing bias and base rate neglect as the pretest probability of COVID-19 infection changes with pandemic surges.

Source: https://casereports.bmj.com/content/14/8/e245210?rss=1