Explain an abnormal newborn bloodspot screen for MPS I (Hurler) — OSCE

Case brief

A two-week-old infant is referred after the newborn bloodspot screen flagged low alpha-L-iduronidase activity, suggesting possible mucopolysaccharidosis type I (Hurler syndrome). The parents have searched online and are distressed by what they have read about progressive coarsening, developmental decline, and early death. They do not understand what a screening test is, why a screen can be wrong, or what confirmatory testing and a possible stem cell transplant would involve. [1] [2]

Task: Counsel the parents. In the course of the eight-minute station, address: (1) what a screening test is and why it must be confirmed, including pseudodeficiency and attenuated variants; (2) what the confirmatory pathway is and over what timeframe; (3) what Hurler syndrome is and what it would mean for their child if confirmed; (4) the role and timing of haemopoietic stem cell transplant or gene therapy, and why it must come before cognitive decline; and (5) the reproductive implications for future pregnancies. [1] [4]

Examiner focus: The candidate should convey uncertainty honestly without catastrophising, distinguish a screen from a diagnosis, set a clear and time-sensitive confirmatory plan, explain the disease-modifying window, and offer genetic counselling for the family — all in plain language the parents can act on. [2] [3]