INTRODUCTION: Acute disseminated encephalomyelitis (ADEM) is a rare immune-mediated condition affecting the central nervous system, characterized by acute encephalopathy and multifocal neurological deficits. This disorder predominantly impacts children but here, we document a rare adult case, emphasizing the necessity for considering organic causes in psychiatric symptomatology. AIMS / OBJECTIVES: A detailed review of literature was conducted through PubMed focusing on the atypical presentations of ADEM and the incidence of organic diseases manifesting psychiatric complaints. This approach informed our diagnostic strategy and management of an unusual adult case of ADEM, underscoring the importance of maintaining a wide differential diagnosis in emergency medicine. CASE DESCRIPTION: A 22-year-old female presented with generalized weakness, confusion, apathy, and reduced appetite, following an upper respiratory tract infection and a distressing dental visit. Her neurological examination revealed dysarthria, dysmetria, and ataxia, with a significant reduction in motor strength and generalized hyperreflexia. Laboratory tests were largely unremarkable except for elevated ESR and CRP. MRI findings were consistent with a demyelinating process, See Figure 1A and 1B, fulfilling the criteria for ADEM diagnosis. RESULTS: Results: Initiation of a steroid regimen led to significant clinical improvement, and by day 11 of hospitalization, there was a marked improvement in the patient's condition, enabling discharge with outpatient neurology and ophthalmology follow-ups. A six-week steroid taper was prescribed. Follow-up MRI confirmed resolution of the demyelinating lesions, confirming the effectiveness of the treatment protocol. DISCUSSION: This case underscores the complexity of diagnosing ADEM in adults, particularly when presenting with psychiatric symptoms. It highlights the critical importance of comprehensive evaluation in emergency settings to identify rare organic causes of psychiatric presentations. This report reinforces the need for awareness among clinicians to consider ADEM in differential diagnoses, ensuring timely and appropriate management for affected patients.

Keywords: Adult Onset Acute Disseminated Encephalomyelitis (ADEM), Case Repot, weakness, confusion, neurological emergency, altered mental status, emergency Medicine.