C2 deficiency represents the most frequent type of a complement deficiency. Clinical manifestation includes infections caused by encapsulated bacteria (Steptococcus pneumoniae, Neisseria meningitidis) such as meningitis, gonitis, pneumonia or septicaemia. A causative treatment has not been available yet. A prophylactic vaccination and/or a long-term antibiotics prophylaxis are recommended. Here we report 2 patients from 2 unrelated families. The first patient suffered from recurrent otitis in his childhood. He underwent osteomyelitis, meningitis complicates with hear-loss, and one episode of pneumonia during adulthood. The second index patient underwent uncomplicated meningitis in his preschool age. He has been treated for recurrent upper-airways infections later. His sister has been completely asymptomatic. The deletion 28 bp (c.841-849+19del28) in C2-gene was detected in all of them in homozygous form. Our paper highlights the variability of a clinical manifestation in homozygous carriers, ranged from asymptomatic cases to patients with history of severe complications. The diagnosis is frequently made even in adulthood.
Keywords: C2; complement system; immunodeficiency; meningitis; pneumococcal disease; vaccination.