Drawing a pedigree can be helpful in identifying patterns of inheritance (Table 1).
Record the date on which the pedigree is drawn and update it as new information becomes available. At each step, ask about the health of the family member being discussed. It may not always be possible to complete the pedigree because of complexities such as adoption, a lack of reliable information or family disruption. It is important to consider such issues in each family. Step-by-step instructions for drawing a pedigree is shown in Table 2.
Step-by-step instructions for drawing a pedigree3