Although SCID is the most common presentation, other clinical phenotypes are described including atypical SCID with hyper IgM [18•], Omenn syndrome [19], progressive CID presenting from later infancy and typified by recurrent infection of the gastrointestinal or sino-respiratory tracts, T- and B-lymphocytopaenia, hypogammaglobulinaemia and autoimmune cytopaenias, some with EBV-associated B lymphomas [20, 21], and antibody deficiency with a common variable immunodeficiency phenoytype [22]. The gene discussed is CD40LG; the disease is severe combined immunodeficiency.