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We wished to determine the influence of parental age at the birth of a retinoblastoma patient on the risk of sporadic hereditary retinoblastoma. The parental age at birth of 941 patients of the Dutch retinoblastoma register was identified and compared between sporadic hereditary and nonhereditary patients. In a subcohort , a comparison was made with parental age at birth in the general population, as obtained from the Central Bureau of Statistics. Missing birth dates of the parents of retinoblastoma patients were traced with the help of the municipal registries and the Central Bureau of Genealogy. The mean paternal age was 10.7 months higher and the mean maternal age was 11.0 months higher in the sporadic hereditary retinoblastoma patients than in parents of nonhereditary patients. In the subcohort, the mean paternal and maternal ages of sporadic hereditary patients were also higher (12.4 and 11.5 months, respectively) than those of the general population. All differences were statistically significant. This study shows that a high parental age is associated with an enhanced risk of sporadic hereditary retinoblastoma. IntroductionRetinoblastoma is a malignant pediatric tumor affecting the retina and occurring about once in 20 000 live births. Retinoblastoma occurs in a hereditary form (30%-40% of the patients) and a nonhereditary form (60%-70%; Vogel 1979). It develops following at least two (Knudson 1971; DerKinderen 1987) mutational events, namely, inactivation of both alleles of the retinoblastoma (RB1) gene at 13q14 (Cavenee et al. 1983;Dryja et al. 1986).The hereditary form results from a germline mutation which is present in all body cells. Among hereditary cases, a familial hereditary form and a sporadic hereditary form may be distinguished. An indication for the familial hereditary form is a parent with retinoblastoma or a family member with this disease, indicating that one of the parents must be a carrier of the RB1 gene. In the sporadic hereditary form, no other family members are affected, and the patient is the first person in the family with retinoblastoma. In the nonhereditary form, the retinoblastoma mutation is exclusively found in the tumor cells of the retina (Knudson 1971;Vogel 1979).Epidemiological observations suggest that parental age is related to the genesis of sporadic hereditary disorders such as Down's syndrome and achondroplasia. This is understandable, since the number of new mutations in germline cells increases with age (Penrose 1955;Vogel and Rathenberg 1975;Vogel 1979). The existence of an association of sporadic hereditary retinoblastoma with parental age is still controversial (Falls and Neel 1951;Stevenson and Martin 1957;Smith and Sorsby 1958;Macklin 1960;Matsunaga 1965;Fraser and Friedmann 1967;Tünte 1972;Pellié et al. 1973;Bunin et al. 1989;Matsunaga et al. 1990; DerKinderen et al. 1990). Furthermore, DNA investigations on some patients suggest that new germline mutations are principally of paternal orgin (Ejima et al. 1988;Dryja et al. 1989;Zhu et al. 1989). Th...
We wished to determine the influence of parental age at the birth of a retinoblastoma patient on the risk of sporadic hereditary retinoblastoma. The parental age at birth of 941 patients of the Dutch retinoblastoma register was identified and compared between sporadic hereditary and nonhereditary patients. In a subcohort , a comparison was made with parental age at birth in the general population, as obtained from the Central Bureau of Statistics. Missing birth dates of the parents of retinoblastoma patients were traced with the help of the municipal registries and the Central Bureau of Genealogy. The mean paternal age was 10.7 months higher and the mean maternal age was 11.0 months higher in the sporadic hereditary retinoblastoma patients than in parents of nonhereditary patients. In the subcohort, the mean paternal and maternal ages of sporadic hereditary patients were also higher (12.4 and 11.5 months, respectively) than those of the general population. All differences were statistically significant. This study shows that a high parental age is associated with an enhanced risk of sporadic hereditary retinoblastoma. IntroductionRetinoblastoma is a malignant pediatric tumor affecting the retina and occurring about once in 20 000 live births. Retinoblastoma occurs in a hereditary form (30%-40% of the patients) and a nonhereditary form (60%-70%; Vogel 1979). It develops following at least two (Knudson 1971; DerKinderen 1987) mutational events, namely, inactivation of both alleles of the retinoblastoma (RB1) gene at 13q14 (Cavenee et al. 1983;Dryja et al. 1986).The hereditary form results from a germline mutation which is present in all body cells. Among hereditary cases, a familial hereditary form and a sporadic hereditary form may be distinguished. An indication for the familial hereditary form is a parent with retinoblastoma or a family member with this disease, indicating that one of the parents must be a carrier of the RB1 gene. In the sporadic hereditary form, no other family members are affected, and the patient is the first person in the family with retinoblastoma. In the nonhereditary form, the retinoblastoma mutation is exclusively found in the tumor cells of the retina (Knudson 1971;Vogel 1979).Epidemiological observations suggest that parental age is related to the genesis of sporadic hereditary disorders such as Down's syndrome and achondroplasia. This is understandable, since the number of new mutations in germline cells increases with age (Penrose 1955;Vogel and Rathenberg 1975;Vogel 1979). The existence of an association of sporadic hereditary retinoblastoma with parental age is still controversial (Falls and Neel 1951;Stevenson and Martin 1957;Smith and Sorsby 1958;Macklin 1960;Matsunaga 1965;Fraser and Friedmann 1967;Tünte 1972;Pellié et al. 1973;Bunin et al. 1989;Matsunaga et al. 1990; DerKinderen et al. 1990). Furthermore, DNA investigations on some patients suggest that new germline mutations are principally of paternal orgin (Ejima et al. 1988;Dryja et al. 1989;Zhu et al. 1989). Th...
No abstract
Mutations may arise throughout an organism's life cycle. Typically, sporadic meiotic mutations give rise to individuals with all their germinal and somatic cells bearing the mutant gene. These mutations may be amorphs (with full penetrance and expressivity) or hypomorphs (with reduced penetrance and expressivity). Mutational mosaicism, however, involves the origin of mutations occurring during mitosis, whether in the parent at some stage prior to reproductive maturity or in the offspring at some time following fertilization. The phenotypic expression and transmission of these new mutations are dependent on the proportion of cells bearing the mutant gene as well as the location of these cells in somatic and/or germinal tissues. Mutational mosaicism was used as a developmental model to analyze 1,500 sporadic and 179 familial cases of retinoblastoma from the world literature. This model provided an interpretation for the origin, onset, and transmissibility of the sporadic unilateral retinoblastoma cases, which represent over 60% of all retinoblastoma patients. The model also permits a reclassification of all transmissible types of retinoblastoma; based on this classification, more accurate risk figures for genetic counseling can be offered. In addition, mutational mosaicism can be extended as a model to other autosomal dominant and X-linked mutations.
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