A 35-year-old man presents to the clinic with a 3-month history of progressive fatigue, unintentional weight loss, and diffuse arthralgias. He also reports intermittent low-grade fevers and night sweats. Physical examination reveals generalized, non-tender lymphadenopathy and a newly auscultated grade 3/6 holosystolic murmur at the cardiac apex. Laboratory studies show a normocytic, normochromic anemia, an elevated erythrocyte sedimentation rate, and a positive rheumatoid factor. Arrange the following differential diagnoses in order from most likely to least likely based on the patient's clinical presentation.
- 1Subacute infective endocarditis
- 2Systemic lupus erythematosus
- 3Adult-onset Still's disease
- 4Acute rheumatic fever
Answer
The most likely diagnosis is subacute infective endocarditis, followed by systemic lupus erythematosus, adult-onset Still's disease, and acute rheumatic fever.
The correct order prioritizes subacute infective endocarditis as the most probable diagnosis because it accounts for the entire clinical picture: a subacute course of constitutional symptoms, a newly auscultated heart murmur (likely mitral regurgitation), and immunologic phenomena such as a positive rheumatoid factor. Systemic lupus erythematosus is ranked second; it can cause similar systemic symptoms and a positive rheumatoid factor, but a new holosystolic murmur is less characteristic. Adult-onset Still's disease is ranked third because, while it causes fever and arthralgias, it is classically seronegative. Acute rheumatic fever is ranked lowest as it generally presents as an acute illness in children following a streptococcal infection, making it highly inconsistent with a 3-month insidious course in a 35-year-old patient.
Step-by-Step Solution
Key Concept
Subacute infective endocarditis is a 'great masquerader' that can present with constitutional symptoms, a new heart murmur, and immunologic phenomena such as a positive rheumatoid factor, frequently mimicking systemic autoimmune diseases.