Subcutaneous Nodules in Acute Rheumatic Fever: Identifying the False Statement
The false statement is A: subcutaneous nodules do NOT appear as evanescent, appearing and disappearing before the examiner's eyes—this description applies to erythema marginatum, not subcutaneous nodules. 1
Why Option A is Incorrect
The American Heart Association clearly distinguishes between the two skin manifestations of acute rheumatic fever:
- Erythema marginatum is the evanescent rash that can appear and disappear, is induced by heat, and blanches with pressure 1
- Subcutaneous nodules are firm, painless, mobile lumps that persist for weeks to months, not fleeting lesions 1
This is a critical clinical distinction that prevents misdiagnosis. Research confirms that subcutaneous nodules typically persist for 4 weeks in 69% of cases, 5-8 weeks in 19%, and can even last 9-12 weeks or longer despite treatment 2. This prolonged duration directly contradicts the "evanescent" description in option A.
Why the Other Statements Are TRUE
Option B: Painless, Small Nodules Over Bony Prominences (TRUE)
- The American Heart Association describes these as firm, painless protuberances found on extensor surfaces over specific joints including knees, elbows, wrists, occiput, and along spinous processes 1
- They are small (typically 0.5-2 cm), mobile lumps beneath the skin overlying bony prominences 1
Option C: Delayed Manifestation at 2-3 Weeks (TRUE)
- Signs and symptoms of acute rheumatic fever, including subcutaneous nodules, develop 2-3 weeks following pharyngitis 3
- This timing aligns with the general 14-21 day post-infection window for all ARF manifestations 4
Option D: Commonly Associated with Carditis (TRUE)
- The American Heart Association notes that nodules are more often observed in patients who also have carditis 1
- Research demonstrates carditis association in 90.4% of cases with subcutaneous nodules 2
- Subcutaneous nodules almost never occur as the sole major manifestation of ARF 1
Clinical Pitfall to Avoid
The most common error is confusing the transient nature of erythema marginatum with the persistent nature of subcutaneous nodules. While erythema marginatum can literally appear and disappear during examination (especially with heat application), subcutaneous nodules are firm, palpable structures that remain for weeks despite appropriate anti-inflammatory treatment 1, 2.