X-linked hyper-immunoglobulin M syndrome: molecular genetic study and long-time follow-up of three generations of a Chinese family.

BACKGROUND

X-linked hyper-immunoglobulin M (IgM) syndrome (XHIGM) is a rare immunodeficiency disease caused by mutations of the CD40 ligand gene. Patients are subject to recurrent infections and have normal or elevated levels of IgM but markedly decreased serum IgG.

OBJECTIVE

We describe molecular genetic studies and clinical manifestations in three generations of one family, as well as results of long-term treatment of 2 young men with the disorder.

METHODS

Of 37 living family members, mutational analysis of the CD40 ligand gene was performed in 36 members. Laboratory data for patients and carriers were reviewed.

RESULTS

Four male family members had died of unexplained causes. The 3 patients with XHIGM syndrome and the 5 carriers all had a novel mutation located at Tyr 169 Asn (T526A) in exon 5, the tumor necrosis factor domain of the CD40 ligand gene. In the 3 patients, CD40 ligand expression in activated CD4+ T cells was below 1%. In the carriers, about half of activated CD4+ cells expressed CD40 ligand. One carrier had malignant lymphoma. Long-term (>20 years) intravenous immunoglobulin therapy in 2 patients improved IgG levels but did not fully suppress the high levels of IgM, nor did it prevent late complications (bronchiectasis and sclerosing cholangitis).

CONCLUSIONS

Diagnosis of a genetic immunodeficiency, especially an X-linked disease such as XHIGM syndrome, should prompt a survey of the entire family.