Clinical meaning
Disseminated gonococcal infection (DGI) occurs when Neisseria gonorrhoeae, a gram-negative diplococcus, invades the bloodstream from a primary mucosal infection site (cervix, urethra, pharynx, or rectum) and spreads to distant sites. DGI complicates approximately 0.5-3% of untreated gonococcal infections.
N. gonorrhoeae has evolved sophisticated immune evasion mechanisms that facilitate dissemination: (1) pili undergo phase and antigenic variation, constantly changing their surface proteins to evade antibody recognition; (2) Opa (opacity-associated) proteins mediate attachment to host cells and can be turned on/off through slipped-strand mispairing, altering immune recognition; (3) lipooligosaccharide (LOS) is sialylated with host sialic acid, camouflaging the bacterium from complement-mediated killing; (4) IgA1 protease cleaves secretory IgA, disabling mucosal immunity.
DGI classically manifests in two overlapping clinical phases: 1. Bacteremic/triad phase (60-70% of DGI): migratory polyarthralgia (multiple joint pains that migrate from joint to joint over hours to days), tenosynovitis (tendon sheath inflammation — especially dorsum of hands, wrists, ankles), and dermatitis (characteristic papular, pustular, or hemorrhagic lesions on an erythematous base, typically on distal extremities — often painless, scattered, few in number). Blood cultures are positive in ~30-50% during this phase. 2. Septic arthritis phase (30-40%): purulent monoarticular (occasionally oligoarticular) infection, most commonly involving the knee, wrist, or ankle. Synovial fluid shows >50,000 WBCs with >75% neutrophils. Gram stain is positive in only 25% (low sensitivity), and synovial fluid culture is positive in ~50%.
Risk factors for dissemination include complement deficiency (terminal complement component deficiencies C5-C9 predispose to recurrent neisserial infections), menstruation (cervical os dilation and mucosal disruption facilitate bloodstream invasion), pregnancy, SLE, and HIV.