meningococcemia
Summary
Meningococcemia is a life-threatening bloodstream infection caused by Neisseria meningitidae, a gram-negative diplococcus. It classically presents with fever, hypotension, and a petechial/purpuric rash, and can rapidly progress to septic shock, disseminated intravascular coagulation (DIC), and death if untreated.
Detail
Pathophysiology: N. meningitidis colonizes the nasopharynx and can invade the bloodstream, especially in individuals with terminal complement deficiencies (C5-C9) or asplenia, who are at higher risk for recurrent/severe infections. The organism's endotoxin (lipooligosaccharide) triggers a massive inflammatory cytokine response, leading to vascular endothelial damage, increased capillary permeability, and microvascular thrombosis. This results in the hallmark petechial/purpuric rash due to vessel wall damage and microthrombi formation. Severe cases progress to Waterhouse-Friderichsen syndrome, characterized by bilateral adrenal hemorrhage and acute adrenal insufficiency, compounding shock.
Clinical presentation: Abrupt onset of fever, chills, malaise, and headache, followed by a rash that begins as maculopapular/petechial and can progress to purpura fulminans (large ecchymotic areas with skin necrosis). Signs of meningitis (neck stiffness, photophobia) may or may not be present, as meningococcemia can occur with or without meningitis. Hypotension, tachycardia, and altered mental status indicate progression to septic shock. Labs often show DIC (thrombocytopenia, prolonged PT/PTT, elevated D-dimer, low fibrinogen).
Risk factors: Asplenia, terminal complement deficiency, crowded living conditions (military barracks, college dorms), and unvaccinated status.
Diagnosis: Blood cultures, CSF analysis if meningitis suspected, Gram stain showing gram-negative diplococci, PCR testing.
Management: Immediate empiric antibiotics (ceftriaxone or penicillin G) without delay for confirmatory testing due to rapid progression; supportive care for shock; close contacts require chemoprophylaxis (rifampin, ciprofloxacin, or ceftriaxone).
Prevention: Meningococcal vaccines (MenACWY and MenB) are key preventive measures, particularly important for adolescents, college students, military recruits, and asplenic/complement-deficient patients.
High-yield associations: Waterhouse-Friderichsen syndrome (adrenal hemorrhage), DIC, association with complement deficiencies (especially terminal complement C5-C9), and rapid progression from petechiae to purpura fulminans.
Sources
- First Aid for the USMLE Step 1
- Sherris Medical Microbiology
- Harrison's Principles of Internal Medicine
- UpToDate: Clinical manifestations of meningococcal infection
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.