A patient with a history of recent sore throat and dental extraction presents with worsening fatigue, shortness of breath, arthralgia, fever, petechia, new heart murmur, mild splenomegaly, hypotension, tachycardia, hyperthermia, mild proteinuria, and microscopic hematuria, what is the most likely diagnosis?

Diagnosis: Infective Endocarditis

The most likely diagnosis is B. Infective endocarditis, based on the constellation of fever, new holosystolic murmur radiating to the axilla (indicating mitral regurgitation), petechiae, splenomegaly, microscopic hematuria, and recent dental extraction providing a portal of entry for bacteremia. 1

Clinical Reasoning

This patient presents with the classic triad that should immediately raise suspicion for infective endocarditis:

• Fever (38.5°C) with systemic symptoms - Present in up to 90% of IE cases and represents the most common presenting symptom 2, 3
• New cardiac murmur (3/6 holosystolic radiating to axilla) - Found in up to 85% of patients, most commonly due to valvular insufficiency; this specific murmur indicates mitral regurgitation from valve destruction 2, 3
• Peripheral embolic phenomena (petechiae) - These represent septic microemboli from infected valve vegetations lodging in capillary beds 4

Supporting Evidence for Infective Endocarditis

Major diagnostic features present:

• Splenomegaly - A classic immunologic/embolic manifestation of IE 1
• Microscopic hematuria with proteinuria - Indicates glomerulonephritis from immune complex deposition, a recognized renal manifestation of IE 2
• Recent dental extraction - Provides the portal of entry for viridans streptococci bacteremia, which can seed damaged or normal heart valves 5, 6
• Preceding sore throat - May represent Group A streptococcal pharyngitis that could have caused transient valvular damage or provided another source of bacteremia 1

Why Not the Other Options?

A. Lymphoma - While lymphoma can present with fever, splenomegaly, and constitutional symptoms, it does not explain:

• The new cardiac murmur indicating acute valvular pathology
• Petechiae in the distribution seen with septic emboli
• The temporal relationship to dental extraction
• Microscopic hematuria with proteinuria (glomerulonephritis pattern)

C. Group A Streptococcus infection - Although the recent sore throat raises this possibility, isolated streptococcal pharyngitis or soft tissue infection would not explain:

• The new mitral regurgitation murmur
• Splenomegaly
• The two-week progressive course with worsening fever
• The renal findings suggesting immune complex disease

D. Systemic Lupus Erythematosus - While SLE can cause fever, arthralgia, proteinuria, and hematuria, several features argue against this:

• The acute presentation over 2 weeks (SLE typically has a more insidious onset)
• The new holosystolic murmur indicating structural valve damage rather than Libman-Sacks endocarditis (which rarely causes significant regurgitation)
• The clear temporal relationship to dental extraction
• The absence of other typical SLE features (rash, photosensitivity, serositis)

Modified Duke Criteria Application

This patient likely meets criteria for definite IE: 1

Major criteria:

• New valvular regurgitation (holosystolic murmur radiating to axilla)
• Clinical features consistent with IE

Minor criteria:

• Predisposing condition (recent dental extraction with bacteremia risk)
• Fever >38°C
• Vascular phenomena (petechiae)
• Immunologic phenomena (glomerulonephritis with hematuria/proteinuria)

Critical Next Steps

Immediate diagnostic workup: 1, 3

• Obtain at least 3 sets of blood cultures from separate sites before starting antibiotics - This is essential and should never be delayed 1
• Transthoracic echocardiography (TTE) immediately, followed by transesophageal echocardiography (TEE) if TTE is negative but clinical suspicion remains high 1
• TEE has >95% sensitivity for detecting vegetations versus 60-75% for TTE 1

Common Pitfalls to Avoid

• Do not start antibiotics before obtaining blood cultures - This is explicitly contraindicated as it may render cultures negative and obscure the diagnosis 1
• Do not dismiss the diagnosis because of the recent dental extraction - Dental procedures are a well-established risk factor for viridans streptococcal endocarditis, particularly when prophylaxis is not given 5, 6
• Do not wait for "classic" peripheral stigmata - Osler's nodes, Janeway lesions, and Roth spots are considerably less common in modern IE, especially early in the disease course 1

The combination of fever, new murmur, embolic phenomena, renal involvement, and recent dental manipulation makes infective endocarditis the diagnosis until proven otherwise, requiring urgent echocardiography and blood cultures. 1, 2