We characterized 22 meningococcal disease cases due to nongroupable Neisseria meningitidis, a rare cause of invasive disease. Disease presentation and severity were similar to those for serogroupable meningococcal disease. However, 7 (32%) patients had complement deficiency or abnormal complement testing results, highlighting the importance of complement testing for nongroupable cases.
Keywords: Neisseria meningitidis; complement component deficiency; meningococcal disease; nongroupable.