Properdin deficiency

Properdin deficiency, also known as complement component properdin deficiency or factor P deficiency, is a rare primary immunodeficiency disorder caused by mutations in the CFP gene located on the X chromosome. Properdin (factor P) is a positive regulator of the alternative complement pathway, stabilizing the C3 and C5 convertases and thereby enhancing complement-mediated immune defense. When properdin is absent or dysfunctional, the alternative complement pathway is impaired, leaving affected individuals highly susceptible to severe infections, particularly fulminant meningococcal disease caused by Neisseria meningitidis. Three types of properdin deficiency have been described: Type I (complete absence of properdin in serum), Type II (low but detectable levels of properdin), and Type III (normal levels of a dysfunctional properdin protein). All three types confer a markedly increased risk of invasive meningococcal infections, which can present as meningitis, meningococcemia, or septic shock. These infections may occur in otherwise healthy males, often in childhood or young adulthood, and can be rapidly fatal if not promptly treated. The immune system is primarily affected, with the complement system being the specific component compromised. There is no specific cure or replacement therapy for properdin deficiency. Management focuses on prevention and early treatment of infections. Vaccination against Neisseria meningitidis (including conjugate and serogroup B vaccines) is strongly recommended, although vaccine responses may be suboptimal. Prophylactic antibiotics may be considered in some cases. Prompt administration of appropriate antibiotics at the first sign of infection is critical. Affected individuals and their families should receive genetic counseling, and at-risk male relatives should be screened. Education about recognizing early signs of meningococcal disease is an essential component of care.

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