title: Reversible severe combined immunodeficiency phenotype secondary to a mutation of the proton-coupled folate transporter.
abstract: Hereditary folate malabsorption is a rare inborn error of metabolism due to mutations in the proton-coupled folate transporter (PCFT). Clinical presentation of PCFT deficiency may mimic severe combined immune deficiency (SCID). We report a 4-month-old female who presented with failure to thrive, normocytic anemia, Pneumocystis jirovecii pneumonia and systemic cytomegalovirus infection. Immunological evaluation revealed hypogammaglobulinemia, absent antibody responses, and lack of mitogen-induced lymphocyte proliferative responses. However, the absolute number and distribution of lymphocyte subsets, including naïve T cells and recent thymic emigrants, were normal, arguing against primary SCID. Serum and cerebrospinal fluid folate levels were undetectable. A homozygous 1082-1G>A mutation of the PCFT gene was found, resulting in skipping of exon 3. Parenteral folinic acid repletion resulted in normalization of anemia, humoral and cellular immunity, and full clinical recovery. PCFT mutations should be considered in infants with SCID-like phenotype, as the immunodeficiency is reversible with parenteral folinic acid repletion.
authors.affiliation: Division of Immunology, Children's Hospital Boston, Boston, MA, USA. arturo.borzutzky@childrens.harvard.edu
authors.forename: Arturo
authors.initials: A
authors.lastname: Borzutzky
authors.forename: Brian
authors.initials: B
authors.lastname: Crompton
authors.forename: Anke K
authors.initials: AK
authors.lastname: Bergmann
authors.forename: Silvia
authors.initials: S
authors.lastname: Giliani
authors.forename: Sachin
authors.initials: S
authors.lastname: Baxi
authors.forename: Madelena
authors.initials: M
authors.lastname: Martin
authors.forename: Ellis J
authors.initials: EJ
authors.lastname: Neufeld
authors.forename: Luigi D
authors.initials: LD
authors.lastname: Notarangelo
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D005260:Female; D005434:Flow Cytometry; D005492:Folic Acid / Q000097:blood / Q000276:immunology* / Q000378:metabolism; D014644:Genetic Variation; D006801:Humans; D016130:Immunophenotyping; D007223:Infant; D007408:Intestinal Absorption; D002955:Leucovorin / Q000008:administration & dosage; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000276:immunology*; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D058979:Proton-Coupled Folate Transporter; D016511:Severe Combined Immunodeficiency / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D026901:Membrane Transport Proteins; D058979:Proton-Coupled Folate Transporter; C505058:SLC46A1 protein, human; D004247:DNA; D005492:Folic Acid; D002955:Leucovorin