Abstract
Primary immunodeficiencies (PID) are becoming a recognized public health problem worldwide. The most important subgroup of these disorders are the antibody deficiencies. X-linked agammaglobulinaemia was the first described entity of this group and is characterised by early onset of recurrent bacterial infections, profound deficiency of all immunoglobulin isotypes and markedly reduced number of peripheral B-lymphocytes. We report the case of a 10-year old boy with X-linked agammaglobulinaemia caused by a previously non-described mutation in BTK gene with typical clinical presentation but delayed diagnosis. Following diagnosis, substitution therapy with intravenous immunoglobulins was started and the clinical status of the patient improved. We reported a case of X-linked agammaglobulinaemia with delayed diagnosis despite the typical anamnestic signs for primary humoral immunodeficiency. The disease was caused by a previously non-reported mutation in the BTK gene. Measurement of serum immunoglobulins should be performed in all children with recurrent, complicated respiratory infections as a screening test for humoral immunodeficiencies.
Highlights
Primary immunodeficiencies (PID) encompass more than 250 disease entities of different incidence and clinical importance
Primary antibody deficiency syndromes are a group of inherited disorders characterized by an inability to develop clinically effective immunoglobulin production
The disease is caused by mutation in the BTK gene (Xq21.3-Xq22), which encodes hematopoietic specific cytoplasmatic tyrosine kinase (Bruton’s tyrosine kinase) expressed in different blood cells.This molecule is extremely important in the signalling through B-cell receptor
Summary
Primary immunodeficiencies (PID) encompass more than 250 disease entities of different incidence and clinical importance. In the group of humoral immunodeficiencies are those with quite high prevalence, such as selective deficiency of IgA or transient hypogammaglobulinemia of infancy, but on the other hand, there are several syndromes with low prevalence and more severe clinical course. The boy underwent several bacterial pneumonias, sinusitis with complication and recurrent otitis media. Molecular analysis of the causal gene for Bruton’s tyrosine kinase (BTK gene) revealed the mutation in exone 5 in PH (pleckstrin homology) domain This missense mutation p.W124C (g.51465G>C, p.Trp124Cys) leads to the changes of amino acid order in the protein with the subsequent changes in activity of BTK (at the level of DNA: substitution of guanine with cytosine, at the protein level: substitution of tryptophan with cysteine) (Table 1). Larly with intravenous immunoglobulins with significant improvement in clinical status and decrease in infectious complications
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