1. SECTIONS:
2. preface & acknowledgements
3. genetics at a glance
4. contacts, support & testing
5. testing & pregnancy
6. newborn screening
7. cancer in the family
8. cardiovascular conditions
9. chromosomal conditions
10. clotting & bleeding conditions
11. cystic fibrosis
12. diabetes
13. fragile X syndrome and other causes of developmental delay
14. haemoglobinopathies
15. hereditary haemochromatosis
16. neurofibromatosis
17. neurological conditions
18. psychiatric conditions
19. genetics in practice
20. emerging genetic technologies
21. glossary

Autosomal recessive inheritance

eg cystic fibrosis, hereditary haemochromatosis

 

Figure 3

Cystic fibrosis: autosomal recessive inheritance

 

1. When a family member is diagnosed with a condition that follows a pattern of autosomal recessive inheritance, there is often not a family history of the condition, since the mutation has previously only been carried through each side of the family. The pedigree above is an example of what could be obtained from the patient.
   
2. Parents of a child with an autosomal recessive condition are almost always obligate carriers for the mutation involved. The recurrence risk is 1 in 4 for each pregnancy.
   
3. Wide variability in clinical expression is common in many autosomal recessive conditions, even within the same family.
   
4. If there is a family history of a particular autosomal recessive condition, it is likely that it has occurred amongst siblings or cousins, and on average will have occurred in 25% of these children.
   
5. It is important to correct the common misunderstanding that conditions can ‘skip’ generations. In the case of autosomal recessive conditions, affected family members may appear to be scattered across a generation. Obviously this has occurred when two carriers for the condition have had children. The pedigree above in Figure 3 is an example of how carriers for autosomal recessive conditions (indicated by filled circles inside symbols) can produce offspring who are affected by that condition.
   
6. Consanguinity is noted more often among the parents of individuals with rare autosomal recessive conditions. A consanguineous relationship noted in the parents of a patient with an unidentified genetic condition suggests the possibility of an autosomal recessive single gene condition.
   
7. If you notice a family history of an autosomal recessive condition, and would like more information on the condition and/or recurrence risks, contact Genetics Services (see Contacts, support and testing).

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