Objective: Hyperimmunoglobulin M (HIGM) syndromes are primary immunodeficiencies characterized by normal or elevated serum IgM levels with decreased levels of other immunoglobulin isotypes. Over the past decade rapid progress has been made in the molecular and genetic basis of HIGM and five distinct subgroups have been described.

Materials and Methods: Records of patients diagnosed as HIGM were retrospectively reviewed to describe the demographic characteristics, initial clinical presentation, age at onset and diagnosis and family history of immunodeficiency, in addition to basic immunological laboratory parameters, and information about follow-up and outcome of patients. Laboratory analyses included complete blood cell and differentials, serum immunoglobulin levels and immunophenotyping of peripheral blood lymphocytes. Flow cytometric analyses of CD40 and stimulated CD40 ligand (CD40L) expression were performed and compared to healthy controls.

Results: We hereby describe 5 HIGM cases (1 female, 4 male) followed in our unit with a mean duration of 7.2 (median 9 years; min-max: 0.4-11.6) years. The age at diagnosis ranged between 1.3-2.3 years (median 2 years), whereas onset of symptoms was generally during infancy. Four cases were from consanguineous parents. Neither autoimmunity, lymphoma, neutropenia or ectodermal dysplasia were detected in any of cases. Evaluation of CD40 was available in four cases and showed normal expression. Stimulated CD40L expressions were found to be normal in the girl and remarkably lower than healthy controls in three boys. Lung imaging revealed bronchiectasis in three patients. All patients are under intravenous immunoglobulin treatment and antibiotic prophylaxis.

Conclusion: HIGM is associated with an increased risk of severe infections and chronic lung damage. Early-diagnosis and prompt initiation of intravenous immunoglobulin therapy is essential to prevent complications.