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Reversible severe combined immunodeficiency phenotype secondary to a mutation of the proton-coupled folate

Arturo Borzutzky1, Brian Crompton, Anke K Bergmann

  • 1Division of Immunology, Children's Hospital Boston, Boston, MA, USA. arturo.borzutzky@childrens.harvard.edu

Clinical Immunology (Orlando, Fla.)
|September 11, 2009
PubMed

Insights

Hereditary folate malabsorption, a rare metabolic disorder, can mimic severe combined immune deficiency (SCID) in infants. Early diagnosis and parenteral folinic acid treatment can reverse the SCID-like symptoms and restore immune function.

Area of Science:

  • Genetics
  • Immunology
  • Metabolic Disorders

Background:

  • Hereditary folate malabsorption is a rare inborn error of metabolism.
  • It results from mutations in the proton-coupled folate transporter (PCFT) gene.
  • PCFT deficiency can present with symptoms mimicking severe combined immune deficiency (SCID).

Observation:

  • A 4-month-old infant presented with failure to thrive, anemia, and opportunistic infections (Pneumocystis jirovecii pneumonia, cytomegalovirus).
  • Immunological evaluation showed hypogammaglobulinemia and absent antibody responses, resembling SCID.
  • However, lymphocyte subset numbers and distributions were normal, suggesting a non-primary SCID cause.

Findings:

  • Serum and cerebrospinal fluid folate levels were undetectable.
  • A homozygous mutation (1082-1G>A) in the PCFT gene was identified, causing exon 3 skipping.
  • Parenteral folinic acid repletion normalized anemia, immune function, and led to full clinical recovery.

Implications:

  • PCFT mutations should be considered in infants presenting with SCID-like phenotypes.
  • The immunodeficiency associated with PCFT deficiency is reversible with appropriate treatment.
  • This highlights the importance of metabolic screening in unexplained immune deficiencies.

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