Parvovirus B19 Meningoencephalitis in Pediatric B-ALL: A Rare Cause of Acute Encephalitis Syndrome

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Introduction: Langerhans Cell Histiocytosis (LCH) is a rare clonal disorder of dendritic cells that can involve single or multiple organ systems.Thyroid involvement in LCH is extremely rare, and may mimic other thyroid pathologies.Methods: A previously healthy 4-year-old male presented with a gradually progressive anterior neck swelling over three months, along with recurrent wheezing.He was brought to the emergency department with generalized tonic-clonic seizures (GTCS) and signs of severe upper airway obstruction.He was found to be hypothyroid and was intubated for airway protection.Initial neck ultrasonography revealed an enlarged thyroid with altered echotexture and vascularity, along with cervical lymphadenopathy.CT neck and chest identified diffuse bilateral pulmonary cysts.He underwent total thyroidectomy as intraoperatively pus was noted within bilateral lobes of thyroid gland.Results: Histopathological examination revealed features consistent with Langerhans Cell Histiocytosis, confirmed by immunohistochemistry (S100, CD1a, Langerin -positive).He was managed symptomatically.Whole body PET-CT , showed lytic lesion of left scapula confirming a multisystem involvement.He was treated as per LCH-IV protocol, with steroids and vinblastine.Completed 6 weeks of induction, showed complete remission.After which he completed continuation chemotherapy, and end of treatment PET-CT showed complete remission.and is in remission for the past 6 months post treatment.Conclusion: This case highlights an unusual initial presentation of multisystem LCH as suppurative thyroiditis with life-threatening airway compromise.Awareness of such atypical presentations is essential for timely diagnosis and management.Thyroid involvement, although rare, should be considered in the differential diagnosis of pediatric neck masses and airway obstruction.