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Acute Rheumatic Fever: Unusual Presentation With Abdominal Pain and Acute Meningoencephalitis in a 10-Year-Old Boy.

CASE PRESENTATION A 10-year-old boy presented with fever, sore throat, and severe abdominal pain, followed by with diffuse myalgia and polyarthralgia from the fifth day of illness. Physical examination on the sixth day of illness showed fever of 39.4°C, tachycardia of 110 beats per minute consistent with fever, normal blood pressure, abdominal tenderness, and a diffuse pain of muscles and joints (dominantly large joints and spine) on palpation. Therewere no swollen or erythematous joints, and no heart murmur was heard. Laboratory tests revealed increased inflammatory markers: erythrocyte sedimentation rate of 110 mm/h, C-reactive protein level of 205.4 mg/L, and procalcitonin level of 4.21 μg/L. Complete blood cell count showed normal red (4.86 10/L) and white blood cell count (8.4 10/L) with a neutrophilia of 87% in differential, and decreased platelet count (78 10/L). Abdominal ultrasound demonstrated diffuse thickening of the small bowelwall, together with a moderate amount of free peritoneal fluid. Blood cultures were obtained, and empirical therapy with ceftriaxone was initiated. The next day, the patient became hypotensive (90/40 mm Hg) and tachycardic (110 beats per minute, not related to fever), complaining about photophobia and neck pain, with a positive meningeal signs. Cerebrospinal fluid analysis revealed moderate pleocytosis of 533 cells/mmwith neutrophilic predominance (83%), mildly elevated protein concentration (0.72 g/L), and a normal glucose level. Magnetic resonance imaging (MRI) findings of the brain were in conjunction with the diagnosis of meningoencephalitis—there was bilateral involvement of temporo-occipital cortex (Fig. 1), as well as internal and external capsule (Fig. 2) and basal ganglia. Echocardiography showed mild mitral regurgitation, left ventricular ejection fraction of 45%, and a small pericardial effusion of 2 to 3 mm, which together with increased levels of troponin I (initially 5095 ng/mL) set the diagnosis of pancarditis. Rapid antigen detection test from pharyngeal swab was positive for group A Streptococcus (GAS). Initial anti-streptolysin O (ASO) titer was 218 IU/mL, with increasing values on hospital days 5, 15, and 23 (260, 584, and 821 IU/mL, respectively). Microbiological studies from blood and cerebrospinal fluid were negative for various infectious diseases, and systemic autoimmune diseases were