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Paternal isodisomy of chromosome 2 in a child with bile salt export pump deficiency

Isabella Giovannoni1, Alessandra Terracciano, Fabrizio Gennari

  • 1Units of Pathology Molecular Medicine and Neurosciences Hepatic Surgery, Children's Hospital Bambino Gesù, Rome Unit of Pathology, Molinette Hospital, Turin IRCCS Fondazione Stella Maris, Pisa, Italy.

Hepatology Research : the Official Journal of the Japan Society of Hepatology
|February 28, 2012
PubMed

Insights

This study details a child with Progressive Familial Intrahepatic Cholestasis type 2 (PFIC2) due to inheriting a full chromosome 2 from his father. This unique inheritance pattern, called uniparental isodisomy, impacts genetic counseling for rare liver diseases.

Area of Science:

  • Genetics
  • Hepatology
  • Pediatrics

Background:

  • Progressive Familial Intrahepatic Cholestasis type 2 (PFIC2) is a severe inherited liver disease.
  • PFIC2 results from mutations in the ABCB11 gene, which encodes the bile salt export pump (BSEP).
  • Typically, PFIC2 follows an autosomal recessive inheritance pattern.

Purpose of the Study:

  • To investigate the genetic basis of PFIC2 in a pediatric patient.
  • To explore an unusual inheritance pattern of the ABCB11 gene mutation.
  • To assess the implications of this inheritance pattern for genetic counseling.

Main Methods:

  • Clinical, pathological, and molecular studies were conducted on a 5.5-year-old boy with PFIC2.
  • Genetic analysis identified a homozygous pathogenic mutation (p.R832C) in the ABCB11 gene.
  • Paternal and maternal DNA were analyzed to determine the inheritance pattern, ruling out deletion and mosaicism.

Main Results:

  • The patient inherited the ABCB11 mutation homozygously through uniparental isodisomy of chromosome 2.
  • The entire paternal chromosome 2, including the ABCB11 gene locus, was inherited from the father.
  • Maternal contribution of chromosome 2 was absent, and no evidence of gene deletion or somatic mosaicism was found.

Conclusions:

  • This is the first reported case of uniparental isodisomy in a hereditary liver disorder like PFIC2.
  • Uniparental isodisomy can lead to homozygous recessive mutations from heterozygous parents.
  • Identifying this inheritance mechanism is crucial for accurate genetic counseling and recurrence risk assessment.

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