Not only does the common γc portion interact with the IL-2 cytokine, but it is also shared by other leukocyte cytokine receptors (IL-4, IL-7, IL-9, IL-15, and IL-21). The IL2RG gene encodes the γc portion and mutations in the IL2RG gene can cause X-SCID. Interleukin-2 receptor (IL-2R) is made from three parts including IL-2Rα and IL-2Rβ and IL-2Rγ. The most common form of SCID is X-linked SCID (X-SCID), which accounts for 50–60% of cases, characterized by the complete deficiency of mature T and NK lymphocytes and a normal or moderately increased number of B cells with a typical phenotype. Neonates with SCID are usually normal at birth, often remain undiagnosed until life-threatening infections happen. Severe combined immunodeficiency (SCID) consists of a heterogeneous group of heritable defects characterized by serious impairment of cellular and humoral immune systems due to a defect in T-cells development. Clinicians should also bear X-SCID in mind in case of approach to any patient with poor weight gain, unusual allergic or endocrine manifestations, even in the case of a normal or increased level of serum immunoglobulins or T and B cells numbers. PIDs should be considered as the differential diagnosis in any patient with unexplained and bizarre symptoms associated with recurrent infections, allergic and autoimmune manifestations. Antiviral and antibiotic prophylaxis, along with monthly IVIG (intravenous immunoglobulin) was started and the patient was subsequently referred for hematopoietic stem cell transplantation. A nucleotide substitution in exon one of interleukin 2 receptor gamma chain (IL-2RG) gene (c.115 G>A, p.D39N, ChrX: 70,331,275) was reported, based on which the diagnosis of X-liked SCID was confirmed. The total count of CD4+ T lymphocytes, along with their naïve and central memory subpopulations, as well as central memory CD8+ T cells were decreased in flow cytometry. Case presentationĪ 6-year-old male presented with a history of food allergy, productive coughs, and recurrent purulent rhinitis, poor weight gain and hypothyroidism. SCID may be inherited as an autosomal recessive or an X-linked genetic trait. Severe combined immunodeficiency (SCID) is a group of relatively rare primary immunodeficiency disorders (PIDs), characterized by disturbed development of T cells and B cells, caused by several genetic mutations that bring on different clinical presentations.
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