Infectious Diseases 2027

Introduction: Macrophage activation syndrome (MAS) is a life-threatening complication of systemic-onset juvenile idiopathic arthritis (SoJIA). Concurrent bacterial infection can obscure MAS because clinical and laboratory features overlap. Neurological involvement and multiorgan dysfunction further complicate recognition and treatment. We describe severe SoJIA-associated MAS with culture-confirmed Salmonella Typhi bacteraemia a focal seizure and abnormal brain MRI findings.

Case: A 3-year-old girl with 2 months of fever and bilateral knee arthritis presented with pallor lymphadenopathy and hepatomegaly. Knee ultrasonography showed complex effusions. Haemoglobin was 4.4 g/dL and packed red-cell transfusions were required. Ferritin was 139,692.6 ng/mL triglycerides were 698 mg/dL fibrinogen was 108.2 mg/dL and LDH was 3,382 U/L. Bone marrow examination showed macrophages with haemophagocytosis. Blood culture grew Salmonella Typhi and initial procalcitonin was >98.45 ng/mL. Complications included conjugated hyperbilirubinaemia with total bilirubin 9 mg/dL and direct bilirubin 8.1 mg/dL acute kidney injury bradycardia hypothermia and persistent hypertension requiring antihypertensive therapy. A focal seizure prompted neuroimaging. MRI showed multifocal cortical and subcortical T2/FLAIR hyperintensities with gyral thickening and post-contrast enhancement. These findings raised concern for MAS-associated or immune-mediated encephalopathy. Prominent perioptic cerebrospinal-fluid spaces raised concern for increased intracranial pressure. CT showed no significant abnormality. Cerebrospinal-fluid glucose was 44 mg/dL and protein was 45 mg/dL. Treatment comprised intravenous methylprednisolone 30 mg/kg/day for 5 days followed by oral corticosteroids cyclosporine and subcutaneous tocilizumab. Antimicrobial therapy was tailored to culture and susceptibility results. Levetiracetam and hypertonic saline were administered for neurological complications. During treatment ferritin declined to 1,768 ng/mL which represented an approximately 98.7% reduction. LDH fell to 319 U/L fibrinogen increased to 276.7 mg/dL and platelets recovered to 329 × 10⁹/L. Procalcitonin fell to 0.36 ng/mL AST normalised to 25 U/L and bilirubin normalised. Triglycerides decreased to 418 mg/dL. She was discharged in stable condition.

Conclusion: This case underscores the need to evaluate infection and MAS concurrently in children with severe systemic inflammation. Culture-confirmed Salmonella Typhi bacteraemia coexisted with extreme hyperferritinaemia hypofibrinogenaemia hypertriglyceridaemia and marrow haemophagocytosis. Suspected inflammatory neurological involvement and multiorgan dysfunction further complicated the presentation. The focal seizure and MRI abnormalities broadened the clinical picture. Falling ferritin and procalcitonin alongside recovery of fibrinogen platelets and hepatic parameters documented improvement during combined antimicrobial and immunomodulatory treatment. Infection should not automatically exclude MAS and suspected MAS should not delay microbiological evaluation or targeted antimicrobial therapy.

Dr. Himanshu Meena, MBBS, MD (Paediatrics), is a Postdoctoral Fellow in Paediatric Rheumatology at the All India Institute of Medical Sciences (AIIMS), Kalyani, West Bengal, India. His clinical and academic interests include paediatric rheumatology, systemic inflammatory disorders and complex paediatric cases.

Audience Take-away Notes

Recognise macrophage activation syndrome early even when bacterial infection is confirmed. Interpret ferritin, fibrinogen, triglycerides, D-dimer and blood counts together; assess neurological and multiorgan complications promptly; and investigate and treat infection alongside MAS.