SUMMARY:We present the first reported case of systemic infection with Neisseria meningitidis serogroup W-135 sequence type (ST)-11 in Japan. A 44-year-old woman presented with high fever, sore throat, and fatigue and was diagnosed with N. meningitidis bacteremia. The causative strain was identified as serogroup W-135 ST-11 by polymerase chain reaction and multilocus sequence typing. Approximately 1 month after treatment, she developed high fever, dyspnea, chest pain, and shoulder pain due to pericarditis, polyarthritis, and tenosynovitis, which are all relatively common immunoreactive complications of W-135 ST-11 meningococcal infections. This causative strain was the same as that responsible for an outbreak of meningitis among Hajj pilgrims in 2000. The strain is now found worldwide because it can attain a high carriage rate and has a long duration of carriage. We suspect that our patient's infection was acquired from an imported chronic carrier. Meningococcal meningitis is rare in Japan, with an incidence of only approximately 10-20 cases per year since the 1990s. Neisseria meningitidis serogroup W-135 is particularly rare in Japan (1), although it is commonly found in Africa, including the area known as thè`m eningitis belt.'' Serogroup W-135 sequence type (ST)-11 caused an outbreak of meningitis among Hajj pilgrims in Mecca in 2000 (2). To date, only one case of systemic W-135 meningococcal infection has been reported in Japan; however, it was not caused by type ST-11.A 44-year-old woman presented with fever (409 C), sore throat, left shoulder pain, chest pain, fatigue, and non-productive cough without meningeal irritation. She had not traveled to any foreign country. She was admitted to a hospital and was subsequently administered ceftriaxone. Her symptoms improved, and she was discharged on the 6th day of illness. N. meningitidis was isolated from her initial blood and sputum cultures. The minimum inhibitory concentrations of penicillin G and ceftriaxone against this strain were 0.025 and 0.002 mg/ml, respectively. On the 15th day of illness, she developed high fever and was admitted to another hospital. Her symptoms did not improve with oral antibiotic treatment, and she was referred to our hospital on the 21st day of illness. Subsequently, her symptoms almost completely resolved after treatment with nonsteroidal anti-inflammatory drugs and levofloxacin.On the 31st day of illness, the patient developed high fever and chest pain and was readmitted to our hospital. She had tenderness of the left shoulder and bilateral sternoclavicular joint pain, and she was unable to abduct her left arm because of pain. Laboratory testing showed an elevated leukocyte count of 13860 cells/ml and C-reactive protein level of 18.3 mg/dl. Electrocardiography showed low QRS voltage and negative T waves on leads V1 to V4. Chest X-ray and chest computed tomography (CT) showed pericardial and bilateral pleural effusions (Fig. 1A, B). 18 F-fluorodeoxy glucose (FDG) positron emission CT showed abnormal FDG uptake in the effusions, sh...