New Mitral Regurgitation Unveiling Infective Endocarditis in an Adolescent With Mitral Valve Prolapse

History of Presentation

A 14-year-old female patient with a known history of mitral valve prolapse (MVP) and atopic dermatitis in treatment with topical corticosteroids presented to the emergency department with reports of nausea, vomiting, and intermittent fever in the previous weeks. On admission, the examination revealed sinus tachycardia, normal blood pressure, and a normal respiratory rate, whereas laboratory tests showed an increased blood count and a mildly raised C-reactive protein (CRP) value.

Past Medical History

Her last transthoracic echocardiography (TTE) 4 months before admission showed a known MVP in Barlow disease conditioning mild mitral regurgitation (MR) (Figure 1, Video 1). The patient was also affected by atopic dermatitis, which was treated with corticosteroid treatment, and 3 months before admission, she underwent a surgical excision of a benign lesion without reported complications. At that time, no antibiotic prophylaxis was performed.

Differential Diagnosis

On the basis of the patient’s history and clinical presentation, several differential diagnoses were considered. Infective endocarditis (IE) was a primary concern given the known MVP, intermittent fever, and elevated inflammatory markers. However, viral or bacterial gastroenteritis could explain the nausea, vomiting, and systemic symptoms. Additionally, systemic inflammatory conditions, such as Kawasaki disease or rheumatic fever, were also evaluated, particularly in a pediatric patient with fever and an elevated inflammatory response.

Investigations

Further investigations were performed, including serial blood cultures, which resulted in a positive result for methicillin-sensitive Staphylococcus aureus. The initial TTE showed no clear vegetations; however, a new regurgitation jet was found, located at and originating from a different region of the valve when compared with previous serial evaluation in the context of the MVP. Thus, transesophageal echocardiography (TEE) imaging was performed and confirmed the known MVP with worsened MR compared with preadmission findings, with a P3 prolapse causing moderate to severe MR (Figures 2A to 2D, Videos 2 and 3).

In agreement with the microbiologist, considering the high probability of IE and the increased degree of MR despite the absence of vegetations at echocardiographic findings, magnetic resonance imaging of the brain was performed and revealed multiple lesions of possible embolic origin. Additionally, a fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) scan was scheduled, which showed focal tracer uptake corresponding to the mitral valve region and spleen hypermetabolism (Figure 3).

Management

The case was discussed by an endocarditis multidisciplinary team, and IE was considered highly probable. Therefore, according to the modified Duke Criteria, long-term antibiotic treatment was chosen. After serial negative results of blood cultures, the patient was discharged with oral antibiotic treatment, which was continued until the first echocardiographic follow-up.

Outcome and Follow-Up

The patient was re-evaluated in an ambulatory care setting at 1-month follow-up. The TTE and TEE follow-up showed further worsening MR, with an advanced flail of the P3 scallop, likely a sequela of previous endocarditis (Figures 4A to 4D, Videos 4 and 5). However, results of serial blood cultures and CRP testing were negative at 1 month, with no evidence of active vegetations at echocardiographic evaluation.

The patient under follow-up also underwent stress echocardiography (SE) as part of her comprehensive assessment. This imaging showed a normal hemodynamic response without arrhythmias and a preserved functional capacity without signs of hemodynamic maladaptation, with a normal increase of pulmonary pressure at the peak of stress. Thus, after multidisciplinary re-evaluation, surgical intervention was temporarily deferred because of the absence of vegetations, the lack of extravalvular involvement, and the response to SE, all further supporting the decision to continue medical management while maintaining close clinical surveillance.

Discussion

Echocardiography, particularly TEE, represents a cornerstone in the diagnostic evaluation of IE both in native valve endocarditis and prosthetic valve endocarditis.¹ However, subtle changes in valvular regurgitation can be difficult to detect, particularly when distinguishing newly developed lesions from preexisting conditions. Significant new valvular regurgitation on echocardiography as compared with previous imaging represents a major criterion of the revised Duke Criteria.¹ However, differentiating it from chronic MR, especially in patients with underlying valvular heart disease (ie, MVP), poses significant challenges.²

A cursory TTE examination could have mistaken the newly developed eccentric MR jet for the patient’s preexisting central MR. However, meticulous assessment, including TEE, provided crucial diagnostic clarity. The absence of flow convergence at the previously documented MR location suggested an alternative origin of regurgitation, which was confirmed at the P3 segment through TEE, also at 1-month follow-up, where flail with complete eversion of the leaflet was visible. Although PET/CT imaging can provide valuable adjunctive evidence, particularly in cases of prosthetic valve endocarditis, its specificity in native valve infections remains limited.³ False-positive findings may arise in response to inflammatory or degenerative processes unrelated to active infection, thereby potentially leading to diagnostic uncertainty.⁴

In this patient, the diagnosis was primarily established through detailed echocardiographic assessment, which revealed a new eccentric MR jet at the P3 segment, a key distinguishing factor from the patient’s preexisting central MR. Given that the Duke criteria consider new valvular regurgitation a major diagnostic factor for IE, meticulous echocardiographic evaluation played a crucial role in confirming the diagnosis. Complementary imaging techniques, such as ¹⁸F-FDG PET/CT, were useful, providing critical additional information, but not indispensable in reaching definitive diagnostic and therapeutic decisions.

Indeed, this case serves as an important reminder that IE diagnosis is not solely dependent on the presence of vegetations. Although vegetations remain a hallmark of endocarditis, their absence does not exclude the disease, and new regurgitation may be the only detectable sign of valvular involvement. In fact, masses may be absent, particularly in cases where embolism represents the initial sign presentation or when multiple embolic events have already occurred. Another crucial aspect is the importance of serial evaluations in cases of high clinical suspicion, even in the absence of detectable masses. In fact, this case highlights how postendocarditic lesions can be progressive, and the complete flail was detected only at 1-month follow-up.

Despite confirmation of IE, a conservative management strategy was chosen because of several critical factors, including the patient’s young age (14 years), preserved hemodynamic stability and pulmonary pressure during SE,⁵ and the absence of extravalvular involvement (normal left ventricular and atrial size, preserved right ventricular function and pulmonary pressure).

Recent studies emphasized that surgery in IE should be reserved for patients with severe heart failure, uncontrolled infection, large vegetations at risk of embolization, or significant structural damage to the valve or surrounding tissues.⁶ This case highlights the importance of individualized decision making in IE, by balancing the benefits of early surgical intervention against the potential risks, particularly in young patients responding well to medical therapy. Close clinical surveillance remains essential to detect any progression of disease that may warrant reconsideration of surgical management.

Conclusions

This case underscores the critical role of meticulous echocardiographic assessment in diagnosing IE, even in the absence of visible vegetations. The recognition of new regurgitation in our patient with the new eccentric MR jet at P3, distinct from preexisting MR, was key to diagnosis, thus highlighting the importance of detailed image interpretation. Given the patient’s young age, favorable response to antibiotics, and stable SE, a temporaneous conservative approach was justified. This case reinforces that in IE, precise thinking, not just advanced imaging, is the key to accurate diagnosis and optimal management. Additionally, an individualized targeted treatment strategy should always be preferred, to avoid misdiagnosis and guide correct treatment.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

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