Plasma cell leukemia (PCL) is a rare plasma cell disorder characterized by peripheral blood plasmacytosis. We present a patient with altered mentality diagnosed with PCL. A 57-year-old woman visited emergency room presenting altered mentality after two days of vomiting. She was drowsy and could speak only 3 to 4 words. Vital signs were stable, and about 3cm-sized nontender swelling on Rt. frontal skull was noted, while there was no history of trauma. Neurologic examination was nonspecific without any other motor or sensory signs. Laboratory findings were as followings: WBC 50,000/uL, Hb 8.40 g/dL, PLT 134,000/uL, Na/K 137/4.2 mmol/L, ionized Ca 2.35 mEq/L, BUN/Cr 26/1.56 mg/dL, LDH 1662.0 U/L, Total/Direct Bilirubin 3.03/1.58 mg/dL, ALP/AST/ALT 92/186/182 U/L, Total Protein/Albumin 5.9/4.0 g/dL, PT 1.88 (INR), B2 microglobulin 12.90 mg/L. Immunoglobulin levels were in normal. There was no heavy chain increment, but serum kappa light chain was elevated as 200 times as upper normal limit. PB smear showed leukoerythroblastosis with many immature blasts up to 30%. Since the symptom rapidly worsened to severe coma and AKI with anuria developed in a day, CRRT was applied. EEG revealed continuous generalized delta slow activity with triphasic morphology. Abdomen CT scan was normal except a chronic liver disease. Brain MRI revealed no abnormal signal intensity in parenchyme, but there was a 35mm-sized osteolytic enhancing mass through scalp and skull. Bone marrow study showed hypercellularity with markedly increased (68%) immature cells with high N/C ratio and bizzare morphology. Flow cytometry showed blasts were positive for CD38 (99.4%) and CD138 (98.9%). CD19, CD79a were positive in 47.1%, 50.3% respectively, but CD3, CD5 and CD20 were negative. Karyotyping found complex abnormalities including 45,X,-X and t(11;14) (q13;q32). Scalp mass biopsy was positive for CD138. Given with the PB blast count, PCL was diagnosed. The patient was recovered with CRRT then received Velcade, adriamycin, and dexamethasone combination chemotherapy. We demonstrate this case as a rare manifestation of plasma cell disorder. Also, the physician should consider paraproteinemic neuropathy as a cause of atypical neuropathy in such conditions.