title: Pitfalls of "hyper"-IgM syndrome: a new CD40 ligand mutation in the presence of low IgM levels. A case report and a critical review of the literature.
abstract: Here, we report on a male infant with low serum IgG, IgA and IgM levels who suffered from Pneumocystis jirovecii and cytomegalovirus (CMV) pneumonia. The patient was tested to be HIV-negative. Absolute and relative numbers of lymphocyte subsets were normal, excluding the diagnosis of an X-linked agammaglobulinaemia (Bruton's disease). Despite the decreased serum IgM level, an X-linked hyper-IgM syndrome (X-HIGM) was considered. X-HIGM is a rare immunodeficiency usually characterised by recurrent severe opportunistic infections, low serum IgG and IgA, but normal or increased serum IgM. The syndrome is caused by mutations of the CD40 ligand (CD40L) gene. In our patient, CD40L mutation analysis proved a novel mutation at codon 257 associated with non-detectable expression of CD40L on the surface of activated T cells. A literature search revealed that approximately 6.4% of X-HIGM patients had been found to have low serum IgM levels. Our statistical analysis of the IgM levels as reported by different studies arouses suspicion that many patients with low IgM levels may not have undergone diagnostic procedures for X-HIGM. In summary, in this report and critical review of the literature, we described a new mutation of CD40L and highlighted the pitfalls of the diagnosis of X-HIGM.
authors.affiliation: Department of Transplantation Immunology, Institute of Immunology, University Hospital for Pediatric and Adolescent Medicine, University of Heidelberg, Heidelberg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Heinold
authors.forename: B
authors.initials: B
authors.lastname: Hanebeck
authors.forename: V
authors.initials: V
authors.lastname: Daniel
authors.forename: J
authors.initials: J
authors.lastname: Heyder
authors.forename: T H
authors.initials: TH
authors.lastname: Tran
authors.forename: B
authors.initials: B
authors.lastname: Döhler
authors.forename: J
authors.initials: J
authors.lastname: Greil
authors.forename: F-M
authors.initials: FM
authors.lastname: Müller
mesh_terms: D000293:Adolescent; D000328:Adult; D023201:CD40 Ligand / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053306:Hyper-IgM Immunodeficiency Syndrome / Q000097:blood* / Q000235:genetics*; D007075:Immunoglobulin M / Q000097:blood*; D007223:Infant; D053208:Kaplan-Meier Estimate; D008297:Male; D009154:Mutation; D055815:Young Adult
chemical_list: D007075:Immunoglobulin M; D023201:CD40 Ligand