1Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Science, Tehran, Iran
2Division of Clinical Immunology, Department of Laboratory Medicine, Karolinska Institute at Karolinska University Hospital Huddinge, Stockholm, Sweden
Background: Defects in B cell class switch recombination (CSR) are a heterogeneous and yet very uncommon group of disorders which all have a genetic basis uniformly leading to hyper IgM (HIgM) syndrome. Due to the rare frequency of these conditions, a very small number of case series have been conducted on the affected patients. Objective: To shed some light on the morbidity and mortality regarding a relatively large cohort of diagnosed CSR defective Iranian patients. Methods: This study was performed using demographic information, laboratory findings and clinical data obtained from an observation of 33 Iranian patients of different ethnicities referred from all medical centers of Iran to the Children’s Medical Center Hospital, pediatrics center of excellence, Tehran, Iran; of which 28 were males and 5 were females. Results: Our patients mean age at the onset of symptoms was 1.8 ± 0.2 years; they were diagnosed with a mean delay of 4.4 ± 3.3 years and followed for a mean time of 5.7 ± 4.8 years. The most prominent clinical features observed were multi-organ infections, affecting mostly the respiratory system, followed by lymphoproliferative and autoimmune disorders, the latter being of much higher frequency (44%) in our study than the reported frequency in previous reports. The three year survival rate for our enrolled patients was 67.9%. Conclusions: Based on our findings, the most common cause of death in HIgM patients is respiratory failure. The molecular mechanism behind the nature of the CSR defective patients in Iran is more compatible with autosomal recessive mutations rather than X-linked HIgM syndrome which is in contrast with other large cohorts of patients with CSR defect.