Patients referred to ED for suspected Neuroleptic Malignant Syndrome ( NMS) often present with clinical instability and marked biological abnormalities. Understanding their biological profile is essential to support diagnosis and guide early management.To describe the clinical parameters and biological findings observed at ED admission in patients evaluated for suspected NMS.This retrospective, observational, XXcenter study was conducted in the xxx over a five-year period from January 2020 to October 2025. Vital signs, neurological findings, laboratory results—including CPK, LDH, ASAT, renal markers, electrolytes, CRP, hematology—along with ECG data, treatments, and final diagnoses were collected and summarizedOn arrival, vital signs were stable and consciousness was preserved, with normal oxygenation, hemodynamics, and a median GCS of 15.Hyperthermia was present in 19.2% of patients, with a median temperature of 37.1 °C. Pupils were reactive in 88.9% of cases. Extrapyramidal signs remained frequent, including rigidity (45.5%), tremor (19.2%), akinesia (10.1%), and cogwheel rigidity (5.1%). Altered consciousness was noted in 15.2% of patients. Biologically, the profile showed clear signs of muscle injury and metabolic stress. Creatine phosphokinase (CPK) was highly elevated (median 739 IU/L, up to >100,000 IU/L), and lactate dehydrogenase (LDH) was also increased (median 226 IU/L [38–5,572]). Aspartate aminotransferase (ASAT) reached up to 1,812 IU/L, consistent with muscle rather than liver involvement.Renal function was generally maintained, though renal impairment was identified in 8% of patients,with creatinine at 67 µmol/L [7.1–244] ,and urea 4.15 mmol/L [1.2–26.7]. Electrolytes were stable: sodium 140 mmol/L [125–163], potassium 3.9 mmol/L [2.06–5.95], and chloride 105 mmol/L [94.3–137]. Inflammation was mild, with C-reactive protein (CRP) at 7.25 mg/L [0.16–224]. Hemoglobin was 14.2 g/dL, leukocytes 10,500/mm³, platelets 255,000/mm³, and the capillary blood glucose measurement ratio remained stable at 1.10 [1.00–1.21].Clinical presentation was mostly stable, but two major findings were prominent: fever in 19.2% of patients and significant rhabdomyolysis with markedly elevated CPK. Aside from these key abnormalities, other systemic parameters, including electrolytes and renal function (8% impairment), remained largely normal.Suspected NMS cases showed high muscle enzymes with preserved renal function and mild inflammation, helping support early recognition and appropriate management