Beyond Achondroplasia

Growing together with Clara

The paternal age risk factor

 

Achondroplasia occurs as a sporadic and spontaneous mutation in approximately 80% of the cases. So most children with achondroplasia have average height parents. By the other side, when a person with achondroplasia has a child, there is a 50% chance of having a baby with the same condition, once it is an autosomal dominant genetic condition, and dominant mutations always show up.

When a baby is born with achondroplasia, the parents might cross very difficult moments of rejection, blame, pain, revolt, and with questions arising: “Why?”,”What have I done wrong?”.

Is important to stress that you didn´t nothing wrong. It just happened. Genes are the brilliance of life and all animal species have been changing constantly throught millions of years.

Achondroplasia is associated with advanced paternal age.

Paternal age effect mutations and selfish spermatogonial selection: causes and consequences for human disease“. Goriely A, Wilkie AO, Am J Hum Genet. 2012 Feb

In this article: “Advanced paternal age has been associated with an increased risk for spontaneous congenital disorders and common complex diseases (such as some cancers, schizophrenia, and autism), but the mechanisms that mediate this effect have been poorly understood. A small group of disorders, including achondroplasia and thanatophoric dysplasia (FGFR3), are included in the “paternal age effect” (PAE) disorders. 

Quantification of mutations in sperm and testes suggests that the common factor in the paternal age effect lies in the dysregulation of spermatogonial cell behavior, an effect mediated molecularly through the growth factor receptor-RAS signal transduction pathway. 

oogenesis and spermatogenesis[9]

Development phases of the reproductive cells: oogenesis (eggs) and spermatogenesis (sperms). Image credits: Major differences

Spermatogenesis take more steps than oogenesis and that increases the chance of genetic mutations.

In another article you can read that:

“The single point mutations in sperm which are responsible for achondroplasia, an dominant diseases, increase with the man’s age”

In an article of 1995: Effect of paternal age in achondroplasia, thanatophoric dysplasia, and osteogenesis imperfecta“,  it says that: “The paternal ages of nonfamilial cases of achondroplasia (ACH) were compared with those of controls and mean paternal age was highly elevated in ACH, 36.30 +/- 6.74 years in the IPIMC, and 37.19 +/- 10.53 years in the ECLAMC;…

Increased maternal age or birth order in these conditions disappeared when corrected for paternal age. Approximately 50% of ACH cases were born to fathers above age 35 years. For ACH , the increase in relative incidence with paternal age fitted an exponential curve…”

In a very clear vision of what is happening nowardays Reproductive functions of the ageing male, Kühnert B, Nieschlag E., 2004, says that men are being parents much older now and there is the common idea that just women, when older, can provoke problems in late conception.

Further readings:

Selfish spermatogonial selection: evidence from an immunohistochemical screen in testes of elderly menWilkie et al, 2012,

Elemental composition of human semen is associated with motility and genomic sperm defects among older men” Wyrobek AJ et al. Human reproduction 2013

Being a father at older age can be an increased risk factor.  Older mothers can be associated to chromosomal alterations (Down syndrome, for example) and older fathers can be associated to genetic mutations like achondroplasia.

Above all, this is science. Not a judgement. With any guilt and with great devotion, keep doing everything for our child happiness.

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