Retinitis Pigmentosa Significant Increase in Mean Paternal Age In One form

http://www.springerlink.com/content/g32l40643n4xw567/


Josseline Kaplan1 , Dominique Bonneau1, Jean Frézal1, Arnold Munnich1 and Jean-Louis Dufier2

(1) Clinique de Génétique Médicale, Unité de Recherches sur les Handicaps Génétiques de l'Enfant, INSERM U.12, Hôpital des Enfants-Malades, 149, Rue de Sèvres, 15 Paris Cedex, France
(2) Consultation d'Ophtalmologie, Unité de Recherches sur les Handicaps Génétiques de l'Enfant, INSERM U.12, Hôpital des Enfants-Malades, 149, Rue de Sèvres, 15 Paris Cedex, France

Received: 12 December 1989 Revised: 14 March 1990

Summary The clinical course of defective vision and blindness has been investigated in relation to different modes of genetic transmission in a large series of 93 families with retinitis pigmentosa (RP). For autosomal dominant RP, two clinical subtypes could be distinguished according to the delay in macular involvement. In the severe form, macular involvement occurred within 10 years, while in the mild form, macular involvement occurred after 20 years. Interestingly, a significant increase of mean paternal age (38.8 years, mean controls in France = 29.1 years, P < 0.001) was found in this form of RP, a feature which is suggestive of new mutations. For autosomal recessive RP, four significantly different clinical subtypes could be recognized, according to both age of onset and the pattern of development (P < 0.001), namely cone-rod dystrophy and early-onset severe forms on the one hand (mean age of onset = 7.6 years), late-onset mild forms and senile forms on the other. Similarly, two significantly different clinical subtypes could be recognized in X-linked RP, according to both mode and age of onset, which were either myopia (mean age = 3.5±0.5 years) or night blindness (mean age = 10.6±4.1 years, P < 0.001). By contrast, no difference was noted regarding the clinical course of the disease, which was remarkably severe whatever the clinical subtype (blindness before 25 years). In addition, all obligate carriers in our series were found to have either severe myopia or pigment deposits in their peripheral retina. Finally, sporadic RP represented the majority of cases in our series (42%). There was a considerable heterogeneity in this group, and at least three clinical forms could be recognized, namely cone-rod dystrophy, early onset-severe forms and late onset moderate forms. At the beginning of the disease, the hereditary nature of the sporadic forms was very difficult to ascertain (especially between 7–10 years) and only the clinical course could possibly provide information regarding the mode of inheritance. However, the high level of consanguinity, and the high sex ratio in early onset and severe sporadic forms (including cone-rod dystrophy), was suggestive of an autosomal or X-linked recessive inheritance, while increased paternal age in late onset forms was suggestive of autosomal dominant mutations.

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What causes Retinitis Pigmentosa?
Retinitis pigmentosa is an inherited disorder, and therefore not caused by injury, infection or any other external or environmental factors. People suffering from RP are born with the disorder already programmed into their cells. Doctors can see the first signs of retinitis pigmentosa in affected children as early as age 10. Research suggests that several different types of gene mutations (changes in genes) can send faulty messages to the retinal cells which leads to their progressive degeneration. In most cases, the disorder is linked to a recessive gene, a gene that must be inherited from both parents in order to cause the disease. But dominant genes and genes on the X chromosome also have been linked to retinitis pigmentosa. In these cases, only one parent has passed the disease gene. In some cases, a new mutation causes the disease to occur in a person who does not have a family history of the disease. The disorder also can show up as part of other syndromes, such as Bassen-Kornzweig disease or Kearns-Sayre syndrome.

In 1981 Geneticist JM Friedman said it was Good Public Health Policy That Both Men and Women Complete Their Family before age 40

"Thus, it is good public health policy to recommend that both men and women complete their family before age 40, if possible.

JM Friedman in an article called Genetic disease in the offspring of older fathers. Obstetrics & Gynecology 1981:57 745-749


Genetic disease in the offspring of older fathers
JM Friedman


Autosomal dominant genetic diseases may result from the transmission of a trait by a carrier parent or from gene mutation in one of the gametes from which the child develops. The mean age of fathers of affected persons has been found to be greater than expected for several autosomal dominant diseases due to new mutations. To assess the clinical importance of this observation, the relative and absolute frequencies of offspring with autosomal dominant diseases due to mutation in the sperm from fathers of various ages have been calculated. The relative frequency of new autosomal dominant mutations in children increases logarithmically with paternal age during the usual years of fatherhood. The absolute frequency of autosomal dominant disease due to new mutations among the offspring of fathers who are 40 years of age or older is estimated to be at least 0.3 to 0.5%. This risk is many times greater than that for children of young fathers and is similar in magnitude to the risk of Down syndrome among the offspring of 35- to 40-year-old mothers. Thus, it is good public health policy to recommend that both men and women complete their family a before age 40, if possible