How would you tell parents that thier child has a hereditary disease?

Hereditary or infectious disease. We have to present out information on the chosen disease by pretending to address the parents of the child who has this disease. How would you tell the parents? My chosen disease: Osteogenesis ImperfectaHow would you tell parents that thier child has a hereditary disease?
I would just say it. Be honest. Find some material on it. I have never heard of this one. sorry and good luck. Give the facts.

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