PID Resources

X-linked Severe Combined Immunodeficiency (X-SCID)

Definitive

Male patient with either a) engraftment of transplacentally acquired maternal T cells; or b) less than 10% CD3+ T cells, less than 2% CD16/56+ NK cells and more than 75% CD19+ B cells, who has one of the following:

  1. Mutation in the cytokine common gamma chain (γc)
  2. Absent γc mRNA on northern blot analysis of lymphocytes
  3. Absent γc protein on the surface of lymphocytes or lymphocyte cell lines
  4. Maternal cousins, uncles or nephews with severe combined immunodeficiency

Probable

Male patient with less than 10% CD3+ T cells, less than 2% CD16/56+ NK cells and more than 75% CD19+ B cells who has all of the following:

  1. Onset of failure to thrive before one year of age
  2. Serum IgG and IgA more than 2 SD below normal for age
  3. Persistent or recurrent diarrhoea, URI or thrush

Possible

Male patient with greater than 40% CD19+ B cells in the peripheral circulation and one of the following:

  1. Engraftment of transplacentally acquired maternal T cells
  2. Maternal cousins, uncles or nephews with a history of severe combined immunodeficiency

Spectrum of disease

Males with XSCID usually develop persistent respiratory infections, diarrhea, and failure to thrive by 4 months of age and are recognized to have immunodeficiency by 6 or 7 months of age. Candidiasis is common. Many patients have normal serum IgM but IgG and IgA are usually very low. Some but not all patients with engraftment of transplacentally acquired maternal T cells show signs of GVH, such as rash and elevated liver function tests. Occasional patients may develop some autologous T and/or NK cells.

Differential diagnosis

  1. JAK3 deficiency
  2. IL-7Ra deficiency
  3. HIV
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