Severe Combined Immune Deficiency (SCID), JAK3 Type

JAK3 mutations cause an autosomal recessive form of severe combined immune deficiency (SCID) that is clinically indistinguishable from the more common X-linked SCID where the deficient gene encodes the interleukin-2 receptor common gamma chain. Both present early in life with persistent severe viral, bacterial, protozoan or fungal infections and are distinguished from some other types of SCID by the lymphocyte profile which is usually T–, NK–, and B+. In both X-linked and JAK3 deficiency SCID, the interleukin signaling pathways in lymphocytes are defective. JAK3 deficiency can be confirmed by tests demonstrating either the absence of the JAK3 protein or, in the presence of a normal common gamma chain, the failure of lymphoid cells to phosphorylate downstream mediators of activation, such as STAT5, in vitro. Detection of deleterious JAK3 gene mutations on both alleles by sequence analysis also is confirmatory.

Tests Available

Forms and Documents

Test Details

  • Confirmation of the clinical diagnosis
  • Differential diagnosis from other types of SCID
  • Diagnosis of atypical mild JAK3 deficiency
  • Carrier testing in siblings or other relatives
  • Prenatal diagnosis in at-risk pregnancies
  • Capillary Sequencing Reflex to Exon Array


3 weeks
2-5 mL Blood - Lavender Top Tube
Oral Rinse (30-40 mL)|Buccal Swabs


  • 279.2 Combined immunity deficiency
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  1. Candotti, F, et al, 1997, Structural and functional basis for JAK3-deficient severe combined immunodeficiency, Blood 90:3996-4003
  2. Notarangelo L, et al, 2001, Mutations in severe combined immune deficiency (SCID) due to JAK3 deficiency, Hum Mutation 18:255-263