X-linked Ichthyosis (XLI)

  • XLR, defect in steroid sulfatase (STS, arylsulfatase C)
  • Presents around infancy with mild erythroderma and large translucent scales → evolves into adherent brown “dirty” scales over extremities, trunk, neck; variable involvement of flexures, sparing of palms/soles/face
  • Mother (with affected fetus): low/absent estrogen in urine/amniotic fluid → labor fails to progress
  • Other associations: comma-shaped corneal opacities, cryptorchidism (↑ risk of testicular CA)
  • Histology: hyperkeratosis or parakeratosis overlying normal or slightly thickened granular layer
  • Tests: serum lipoprotein electrophoresis (detects accumulation of cholesterol sulfate)