Consanguinity and Genetic Risks: A Clinical Case Study on Dual Diagnosis and Genetic Counselling

Illustrative story—please confirm the findings against the actual case before presenting it as a patient’s experience.

A couple sought genetic advice after their child was diagnosed with both deafness and skeletal dysplasia, a condition affecting bone growth. They wanted to understand whether one disorder could explain everything—and what this meant for another pregnancy.

The Family Background and Consanguinity

Their family history revealed an unusual connection: they were double first cousins. Two brothers from one family had married two sisters from another, and the couple were their children.

Understanding Double First Cousins

They shared both sets of grandparents, making them more closely related than ordinary first cousins, although they were not genetically equivalent to brother and sister.

Genetic Testing and Findings

Genetic testing revealed that their child had two separate recessive disorders: one causing deafness and another causing skeletal dysplasia.

Carrier Screening Results

Expanded carrier screening also showed that both parents carried the same disease-causing variants in three different genes, including those responsible for their child’s conditions.

Clinical Implications and Family Planning

The findings helped explain why their child had two diagnoses and identified an additional reproductive risk.

Next Steps for Reproductive Options

With this knowledge, the couple could discuss targeted prenatal testing or IVF with PGT-M when planning another pregnancy.

Conclusion

For this family, the turning point was understanding that their child’s difficulties had two distinct genetic causes—and that this knowledge could guide their next steps.