Infective Endocarditis Presenting With Scalp Allodynia and a Giant Cell Arteritis-Like Vasculitic Phenotype.

BACKGROUND The clinical manifestations of infective endocarditis (IE) are highly varied, and diagnostic delays are common and potentially life-threatening. Due to their overlapping clinical presentations, IE may be misdiagnosed as giant cell arteritis (GCA). Although IE mimics GCA, scalp allodynia associated with IE has not previously been reported. CASE REPORT A 60-year-old man with mitral valve prolapse presented with fever, generalized stiffness, and low back pain refractory to oral antibiotics and low-dose glucocorticoids. He also reported a stinging sensation on his scalp while washing his hair, consistent with scalp allodynia. Prednisolone was initiated for presumed GCA. However, blood cultures subsequently grew Streptococcus parasanguinis, and imaging studies showed hematogenous dissemination. Ultimately, IE was confirmed based on the modified Duke Criteria. All symptoms, including scalp allodynia, resolved completely following the initiation of antibiotic therapy. CONCLUSIONS This case highlights that scalp allodynia, while characteristic of GCA, can also occur in IE, and underscores the limitations of relying solely on clinical symptoms when differentiating GCA from infectious etiologies. In patients with fever and scalp allodynia-particularly those with predisposing cardiac conditions-IE warrants strong consideration. Blood cultures should be obtained before initiating glucocorticoid therapy, and early clinical reassessment is critical to avoid the potentially catastrophic consequences of missed or delayed IE diagnosis.