complement component 4b deficiency

Complement component 4b deficiency is a condition caused by mutations in the C4B gene that result in reduced levels of a key protein in the complement cascade, an essential part of the immune response. Affected individuals commonly experience recurrent respiratory infections such as pneumonia, otitis media, and sinusitis, as well as asthma and chronic diarrhea. The clinical presentation typically emerges in childhood when these immune-related challenges first become apparent. Although precise information on prevalence is not available, the consistent presence of these symptoms provides a strong indication of the condition.

The clinical features of complement component 4b deficiency are characterized by a persistent pattern of immune-related symptoms. Individuals almost invariably experience asthma, recurrent otitis media, sinusitis, and pneumonia, along with chronic diarrhea and decreased circulating levels of complement C4b. These manifestations often lead to repeated healthcare visits starting in early childhood. Not all individuals experience every feature, and severity varies widely.

This condition is caused by pathogenic variants in the C4B gene, which encodes an important protein in the classical complement pathway that helps defend against infections. Disruptions in the production or function of the C4B protein lead to decreased complement activity, compromising the body’s ability to effectively clear pathogens. The mode of inheritance for complement component 4b deficiency is not clearly defined at this time, and further research is needed to elucidate familial patterns. Genetic counseling may provide additional insight for families regarding the genetic aspects of the condition. Associated genes include C4B.