tokens: We examined the utility of seeking evidence of NRXI to test the carrier status of women in families affected by X-linked severe combined immunodeficiency ( XSCID ) and X-linked hypogammaglobulinaemia ( XLH ) , to identify as carriers the mothers of boys with SCID or hypogammaglobulinaemia whose phenotype suggested X-linkage and to infer X-linkage in boys with SCID or hypogammaglobulinaemia whose disease was not clearly X-linked on the basis either of family history or clinical and immunological characteristics .