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MyD88 deficiency
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

MyD88 deficiency

MyD88 deficiency is an inherited primary immunodeficiency that impairs the innate immune response, leading to frequent and severe infections by pyogenic bacteria.

Overview

MyD88 deficiency is an inherited disorder of the immune system that affects the innate immune response—the body's early, nonspecific defense against pathogens. Affected individuals are susceptible to frequent and severe infections by pyogenic bacteria (bacteria that cause pus production), such as Streptococcus pneumoniae, Staphylococcus aureus, and Pseudomonas aeruginosa.

Symptoms

Most individuals experience their first bacterial infection before age 2. Infections can be life-threatening in infancy and childhood, though they typically become less frequent by age 10. Common clinical presentations include:

  • Invasive bacterial infections, including septicemia (blood infection), meningitis, and arthritis
  • Abscesses on internal organs
  • Localized infections of the ears, nose, or throat
  • Absence of high fever in response to severe infections

Causes

MyD88 deficiency is caused by mutations in the MYD88 gene. The MyD88 protein is a critical component of a signaling pathway involved in the early recognition of pathogens and the initiation of inflammation. Mutations lead to a nonfunctional protein or a total lack of protein, preventing the immune system from triggering the necessary inflammatory response to fight off bacterial invaders. It is believed that as the immune system matures, other biological systems compensate for the loss of MyD88, which explains the clinical improvement often seen by adolescence.

Inheritance

This condition is inherited in an autosomal recessive pattern. Both copies of the gene in each cell must have mutations for the condition to occur. Parents of an affected individual each carry one copy of the mutated gene but typically do not exhibit symptoms.

Frequently Asked Questions

Because MyD88 is essential for Toll‑like receptor signaling that triggers the production of pyrogenic cytokines (like IL‑1 and TNF‑α). When MyD88 is absent, the inflammatory cascade that raises body temperature is blunted, so infections can present with minimal or no fever. Caregivers should watch for other red‑flag signs such as rapid breathing, lethargy, unexplained irritability, swelling, or new skin lesions, and seek medical evaluation promptly.
Live attenuated vaccines (e.g., oral polio, rotavirus, BCG, varicella) are generally avoided because the weakened organisms can cause disease in the setting of impaired innate immunity. Inactivated or subunit vaccines (e.g., pneumococcal conjugate, Haemophilus influenzae type b, meningococcal, influenza) are still beneficial and should be given according to standard schedules, often with close post‑vaccination monitoring. Some clinicians also give additional booster doses of polysaccharide vaccines to improve coverage against pyogenic bacteria.
Many experts prescribe continuous low‑dose prophylaxis (e.g., amoxicillin or a macrolide) especially in early childhood when infection risk is highest. The choice depends on local bacterial resistance patterns, previous infection history, and tolerability. Periodic reassessment is essential; some patients can discontinue prophylaxis after age 10 if infection frequency declines and immune function appears compensated.
Testing usually involves sequencing the MYD88 gene from a blood sample (next‑generation sequencing or targeted Sanger sequencing). Results can reveal homozygous or compound heterozygous pathogenic variants confirming the diagnosis. Because inheritance is autosomal recessive, carrier testing for siblings and genetic counseling for parents are recommended. Prenatal or pre‑implantation testing is possible if the specific family mutations are known.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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