Background and objectives: It has been reported that there is a high prevalence of immunodeficiency and autoimmunity in relatives of patients with common variable immunodeficiency (CVID). The aim of this study was to determine the prevalence of immunoglobulin deficiency in relatives of patients with CVID in Iran, where there is a high rate of consanguineous marriage.

Methods: A descriptive study was undertaken in 64 family members of 23 unrelated CVID patients. The group contained 17 fathers, 18 mothers, 18 sisters, 9 brothers, and 2 children. Serum immunoglobulin levels were measured by nephelometry. Immunoglobulin (Ig) G subclass levels were measured in a subgroup of 36 individuals. Serum IgA levels were confirmed by enzyme-linked immunosorbent assay
for subjects with suspected IgA deficiency.

Results: The rate of consanguineous marriage in families containing relatives with antibody deficiencies was significantly higher than in those families in whom relatives did not have immune defi ciencies. IgA deficiency was observed in 2 relatives of patients with CVID. Also CVID was observed in 2 family members. In 3 fathers and 1 brother, IgM levels were lower than normal. Three relatives had IgG4 deficiency and  1 person had combined IgG4 and IgG2 deficiency. Twenty percent of the relatives had hypogammaglobulinemia (including IgA deficiency, CVID, decreased levels of IgM, and IgG subclass deficiencies).

Conclusion: In our study, alteration in humoral immunity in relatives of CVID patients was higher than previously reported, and this could be attributed to the high rate of consanguineous marriage in Iran. Since the family members of CVID patients are at high risk of hypogammaglobulinemia, it is advisable that they be evaluated for immunodeficiency disorders and monitored throughout their
lifetimes.

Key words: Common variable immunodeficiency. Family members. Immunoglobulin deficiency.