[Hyper-IgM syndrome in members of two unrelated Chilean families: molecular and mutation analysis]

Hyper-IgM syndronie (HIGM) is a rare primary immunodeficiency used to describe a heterogeneous group of disorders characterized by recurrey bacterial infrctions, normal or elevated serum IgM levels and low or absent serum IgG, IgA and IgE.

To make definitive diagnosis, detect mutations in carriers and perform genetic counseling in patients with HIGM.

We studied the expression of CD40L, CD40 and made a mutation analysis of the CD40L gene in 3 males of 2 unrelated Chilean families diagnosed as a possible syndrome of hyper-IgM and 3 relatives.

We identified a deletion frameshift in the exon 2 (delA225) of the extracellular domain of GD40L gene in one patient and verified the carrier stains of his mother and sister. The other patients showed a low expression of GD40L in activated T cells (65.3% ammd 65.5%) and a normal expressiomi of CD40. No alterations were found in the single strand conformation polymorphism analysis of the CD40L.

These result allowed us to make a definite diagnosis of HIGM1 of a patient, detect female carriers and suggest a HIGM of recessive inheritance with normal CD40 expression in the patients of the second family.