The risk for recurrence of germinal (gonadal) mosaicism is conditional on the fact that one of the parents is a germinal mosaic and can be determined from the number of affected children, number of unaffected children with the at risk chromosome, and the number of untyped children who are unaffected.
Mosaicism is the presence of 2 or more cell lines with different genotypes occurring in a single zygote or embryo after conception. In germline mosaics a fraction of the gonadal cells will have the mutation. The fraction of gonadal cells and the recurrence risk are dependent on the gonadal generation in which the mutation occurred, with the maximum recurrence risk being 50%. The recurrence risks for germinal mosaicism is almost constant for gonadal generation values of 20 or more.
The equation for generating these tables is seen on page 103, van der Meulen et al (1995).
1 Affected Child
|
Risk of Recurrence |
Number of Typed Unaffected Children with the At Risk Chromosome |
||||
|---|---|---|---|---|---|
|
Number Untyped Unaffected Children |
0 |
1 |
2 |
3 |
4 |
|
0 |
0.048 |
0.018 |
0.013 |
0.010 |
0.008 |
|
1 |
0.033 |
0.015 |
0.012 |
0.009 |
0.008 |
|
2 |
0.025 |
0.013 |
0.010 |
0.008 |
0.007 |
|
3 |
0.019 |
0.012 |
0.009 |
0.008 |
0.007 |
|
4 |
0.016 |
0.011 |
0.009 |
0.007 |
0.006 |
2 Affected Children
|
Risk of Recurrence |
Number of Typed Unaffected Children with the At Risk Chromosome |
||||
|---|---|---|---|---|---|
|
Number Untyped Unaffected Children |
0 |
1 |
2 |
3 |
4 |
|
0 |
0.333 |
0.143 |
0.120 |
0.100 |
0.084 |
|
1 |
0.286 |
0.133 |
0.111 |
0.093 |
0.079 |
|
2 |
0.240 |
0.124 |
0.103 |
0.087 |
0.074 |
|
3 |
0.200 |
0.115 |
0.096 |
0.081 |
0.069 |
|
4 |
0.168 |
0.107 |
0.089 |
0.075 |
0.065 |
3 Affected Children
|
Risk of Recurrence |
Number of Typed Unaffected Children with the At Risk Chromosome |
||||
|---|---|---|---|---|---|
|
Number Untyped Unaffected Children |
0 |
1 |
2 |
3 |
4 |
|
0 |
0.429 |
0.200 |
0.183 |
0.164 |
0.145 |
|
1 |
0.400 |
0.194 |
0.175 |
0.156 |
0.138 |
|
2 |
0.366 |
0.187 |
0.168 |
0.149 |
0.131 |
|
3 |
0.328 |
0.179 |
0.160 |
0.141 |
0.124 |
|
4 |
0.290 |
0.172 |
0.153 |
0.134 |
0.118 |
4 Affected Children
|
Risk of Recurrence |
Number of Typed Unaffected Children with the At Risk Chromosome |
||||
|---|---|---|---|---|---|
|
Number Untyped Unaffected Children |
0 |
1 |
2 |
3 |
4 |
|
0 |
0.467 |
0.226 |
0.216 |
0.203 |
0.188 |
|
1 |
0.425 |
0.222 |
0.211 |
0.197 |
0.181 |
|
2 |
0.431 |
0.218 |
0.206 |
0.191 |
0.175 |
|
3 |
0.406 |
0.214 |
0.200 |
0.185 |
0.168 |
|
4 |
0.375 |
0.209 |
0.195 |
0.178 |
0.161 |
Specialty: Genetics
