Bloom syndrome

Introduction

Bloom's syndrome (BS) is a chromosomal instability syndrome characterized by photosensitivity & developmental anomalies.

Pathology

• defective cell-mediated immunity & increased susceptibility to infections are observed
• leukemia occurs with higher frequency in BS patients
• spontaneous sister chromatid exchange & chromosome aberrations are found in virtually all BS patients
• reduced levels of DNA ligase are found in cells from patients with BS

Genetics

• autosomal recessive disorder
• defects in the BLM helicase are the cause of Bloom syndrome
• missense mutation in the gene for DNA ligase I is suggested
• p53 mutations are common in transformed cells from BS patients

Clinical manifestations

• photosensitivity of prenatal onset
  • erythema & telangiectasia
    • butterfly distribution on the face
  • facial erythema develops during infancy following exposure to sunlight
  • a bullous eruption may appear on the lips
  • telangiectatic erythema may appear on the hands & forearms
• cafe-au-lait spots, ichthyosis, acanthosis nigricans, & hypertrichosis are less constant cutaneous manifestations
• developmental anomalies
  • dwarfism
  • defective dentition, prominent ears, pilonidal cysts, sacral dimples, syndactyly, polydactyly, clinodactyly of the 5th fingers, shortened lower extremities & club feet are additional inconstant features
  • proportionate pre- & postnatal growth deficiency
• intellect is normal

Laboratory

• BLM gene mutation analysis
• see ARUP consult

Complications

• predisposition to malignancy

More general terms

• chromosomal instability syndrome
• bone marrow disease
• progeroid syndrome

Database

• OMIM: https://mirror.omim.org/entry/210900