Pyogenic bacterial infections due to MyD88 deficiency

Immunodeficiency-68 (IMD68) is an autosomal recessive primary immunodeficiency characterized by severe systemic and invasive bacterial infections beginning in infancy or early childhood. The most common organisms implicated are Streptococcus pneumoniae, Staphylococcus aureus, and Pseudomonas, although other organisms may be observed. IMD68 is life-threatening in infancy and early childhood. The first invasive infection typically occurs before 2 years of age, with meningitis and upper respiratory infections being common manifestations. The mortality rate in early childhood is high, with most deaths occurring before 8 years of age. Affected individuals have an impaired inflammatory response to infection, including lack of fever and neutropenia, although erythrocyte sedimentation rate (ESR) and C-reactive protein may be elevated. General immunologic workup tends to be normal, with normal levels of B cells, T cells, and NK cells. However, more detailed studies indicate impaired cytokine response to lipopolysaccharide (LPS) and IL1B (147720) stimulation; response to TNFA (191160) is usually normal. Patients have good antibody responses to most vaccinations. Viral, fungal, and parasitic infections are generally not observed. Early detection is critical in early childhood because prophylactic treatment with IVIg or certain antibiotics is effective; the disorder tends to improve naturally around adolescence. At the molecular level, IMD68 results from impaired function of selective Toll receptor (see TLR4, 603030)/IL1R (see IL1R1; 147810) signaling pathways that ultimately activate NFKB (164011) to produce cytokines (summary by Picard et al., 2010). See also IMD67 (607676), caused by mutation in the IRAK4 gene (602170), which shows a similar phenotype to IMD68. As the MYD88 and IRAK4 genes interact in the same intracellular signaling pathway, the clinical and cellular features are almost indistinguishable (summary by Picard et al., 2010). [from OMIM]