Evaluation of Patients with Combined Immunodeficiency: A Single Center Experience.

Background: Severe combined immunodeficiency (SCID) is the most severe form of inborn errors of immunity (IEIs) and typically leads to death within the first year of life. Combined immunodeficiencies (CID) are immune disorders that are less severe than SCID and are characterized by qualitative or quantitative defects in T and B cells.

Objective: To explore the clinical, laboratory, and genetic diagnostic approaches for patients diagnosed with SCID and CID.

Methods: In this retrospective single-center study, we evaluated 54 patients diagnosed with SCID and CID between 2006 and 2019.

Results: The male to female ratio was 30:24 and the rate of consanguinity was 77.8%. Among the patients, 23 were diagnosed with SCID and 31 diagnosed with CID. The most common phenotype in the SCID group was T-B-NK+ while in the CID group it was MHC class II deficiency. The median age at symptom onset for SCID and CID were 1 month and 5 months, respectively, while the median age at diagnosis was 4 months for SCID and 11 months for CID. The age at diagnosis of SCID and the age at diagnosis of symptoms were earlier than CID (p<0.05). Lymphopenia was present in 90.9% of patients with SCID and 51.6% of patients with CID (p<0.05). HSCT was performed in 10 out of 23 (43.4%) SCID patients and 10 out of 31 (32.2%) CID patients (total of 20 out of 54, 37%). The survival rates of SCID and CID patients who underwent HSCT were 80% and 70%, respectively.

Conclusion: Consanguineous marriage, sibling death and family members with similar characteristics should be investigated for early diagnosis. Further investigations should be performed in the presence of lymphopenia. With the increasing number of genetic diagnosis facilities and HSCT centers, the survival rate of patients is expected to rise.