Cohort of Iranian Patients with Congenital Agammaglobulinemia: Mutation Analysis and Novel Gene Defects

<p><b>Objectives:</b> Impairment in early B-cell development can cause a predominantly antibody deficiency with severe depletion of peripheral B-cells. Mutations in the gene encoding for Bruton’s-tyrosine-kinase (BTK) and the components of the pre-B-cell receptor complex or downstream signaling molecules have been related to this defect in patients with agammaglobulinemia.</p> <p><b>Methods:</b> Iranian patients with congenital agammaglobulinemia were included and the correlation between disease-causing mutations and parameters such as clinical and immunologic phenotypes were evaluated in available patients.</p> <p><b>Results:</b> Out of 87 patients, a molecular investigation was performed on 51 patients leading to identification of 39 cases with BTK (1 novel mutation), 5 cases of µ-heavy chain (3 novel mutations) and 1 case of Igα-deficiencies.</p> <p><b>Conclusion:</b> Although there is no comprehensive correlation between type of responsible <i>BTK</i> mutation and severity of clinical phenotype, our data suggest that BTK-deficient and autosomal recessive agammaglobulinemia patients differ significantly regarding clinical/immunologic characteristics.</p

Table indicating the clinical presentations of TB recorded in the fifty patients.

<p>The two patients presenting with IL-12Rβ1 deficiency are in bold. N means number and age is indicated in years.</p

Mendelian mutations in <i>IL12RB1</i> leading to severe tuberculosis in two kindreds.

<p><b>A</b>. Pedigree of the two families (A and B) with IL-12Rβ1 deficiency. Each generation is designated by a roman numeral (I–II), and each individual by an Arabic numeral. The double lines connecting the parents indicate consanguinity. The probands are indicated by an arrow, with black indicating <i>Mycobacterium tuberculosis</i> disease status. Individuals whose genetic status could not be evaluated are indicated by the symbol “E?”. <b>B</b>. Electrophoregram showing the genomic sequences of exons 9 and 5 in patients 1 and 2, respectively, compared with a control sequence. <b>C</b>. Schematic diagram of the coding region of the IL-12Rβ1 chain containing 17 coding exons and encoding a 662-amino acid protein with a leader sequence (exon1, L), extracellular domain (exons 2 to 13, EC), transmembrane domain (exon 14, TM) and an intracellular cytoplasmic domain (exons 15 to 17, IC). Published and unpublished mutations are indicated as follows: missense mutations are shown in purple, nonsense mutations are shown in red and complex mutations are shown in brown. Splicing mutations are shown in blue, large deletions are shown in green, insertions are shown in orange, and duplication is shown in magenta. * The 700+362_1619-944del mutation is the only mutation resulting in at the expression of a protein at the cell surface. Mutations of P1 (K305X) and P2 (R173W) are underlined. <b>D</b>. Chest X ray of patient 1 showing the localization of the disease.</p