The clinical significance of complete class switching defect in Ataxia telangiectasia patients.
Ataxia telangiectasia (AT) is a primary immunodeficiency associated with recurrent infections. We aimed to investigate clinical and immunological classification in AT patients who suffer from a different spectrum of humoral immune defects.



AT patients were categorized according to the ability of class switching and patients with hyper IgM (HIgM) profile were defined as class switching defect (CSD).



Serum immunoglobulin profile in 66 AT patients showed normal immunoglobulin level (22.8%), IgA deficiency (37.9%) and hypogammaglobulinemia (18.1%) in the majority of patients, while 21.2% had HIgM profile revealing CSD. CSD does not affect the frequency of infections, however, the frequency of lymphoproliferation (p < 0.001), and autoimmunity (p = 0.004) were significantly higher in this group. Neurologic symptoms in CSD patients are mild or appear after recurrent infections, therefore these patients were usually misdiagnosed as HIgM syndrome.



Although most of AT patients have reduced IgA levels or normal immunoglobulin levels, but a fraction of these patients may show CSD ensuing HIgM-profile. CSD poses affected individuals at higher risk of non-infectious complications.
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.
Saleh
S
Ghiasy
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.
Leila
L
Parvaneh
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.|b Department of Laboratory Medicine, Imam Hassan Mojtaba Hospital , Alborz University of Medical Sciences , Karaj , Iran.
Gholamreza
G
Azizi
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.
Ghazal
G
Sadri
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.
Majid
M
Zaki Dizaji
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.|c Division of Clinical Immunology, Department of Laboratory Medicine , Karolinska Institutet at Karolinska University Hospital Huddinge , Stockholm , Sweden.
Hassan
H
Abolhassani
a Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center , Tehran University of Medical Sciences , Tehran , Iran.
Asghar
A
Aghamohammadi
D001260:Ataxia Telangiectasia / Q000175:diagnosis* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D003241:Consanguinity; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D053306:Hyper-IgM Immunodeficiency Syndrome / Q000175:diagnosis* / Q000276:immunology; D007070:Immunoglobulin A / Q000097:blood; D017578:Immunoglobulin Class Switching; D007075:Immunoglobulin M / Q000097:blood; D007239:Infections / Q000175:diagnosis* / Q000276:immunology; D007492:Iran; D008297:Male; D012189:Retrospective Studies
D007070:Immunoglobulin A; D007075:Immunoglobulin M
Ataxia telangiectasia; IgA deficiency; class switching defect; humoral immune defects; hyper IgM syndrome; hypogammaglobulinemia; immune deficiency; infection