Streptococcus mitis Cellulitis Progressing to Severe Sepsis, Septic Shock, and Suspected Toxic Shock Syndrome in a Previously Healthy Child.

Streptococcus mitis (S. mitis), a commensal member of the viridans group streptococci (VGS), is usually low virulence but can rarely cause severe invasive infections such as streptococcal toxic shock syndrome (STSS). We report the case of a previously healthy four-year-old girl who initially presented with atraumatic right-leg pain and rapidly developed extensive cellulitis, severe sepsis, and septic shock. Despite early ceftriaxone therapy, she deteriorated with fever, hypotension, metabolic acidosis, and progressive spreading of erythema. She required paediatric intensive care unit (PICU) admission for aggressive fluid resuscitation and vasoactive support with adrenaline, dobutamine, and later milrinone. Broad-spectrum antibiotics and clindamycin were given for toxin suppression. Echocardiography revealed a reduced ejection fraction (EF) with biventricular dilation, prompting the administration of intravenous immunoglobulin (IVIG) for suspected myocarditis. Blood cultures confirmed S. mitis sensitive to multiple antimicrobials. After eight days of intensive care, the patient improved with the resolution of cellulitis and hemodynamic stabilization. This case highlights the rare ability of S. mitis to cause toxin-mediated shock in healthy children and emphasizes the importance of early recognition and aggressive management.