Congenital, hereditary and familial, difference?

[sameeralord]

Hello everyone,

I thought I understood these terms, but got confused lately .

My understanding

Congenital- Present at birth
Familial: Occuring in family or its members
Hereditary: Transmitted or capable of being transmitted genetically from parent to offspring

My questions

1. Ok congenital means disease it present at birth. In familial and hereditary also the abnormal genes are present at birth if so why don't their diseases present at birth, why do they manifest later in life?

2. Are all familial diseases hereditary? I really can't differentiate these. Any examples

3. Also aren't some congenital diseases, hereditary/familial? Any examples.

4. Also in some classifications I have seen in textbooks. They take familial causes, under acquired causes section.How is familial and acquired cause, when it is genetic?

Thanks

 

[galadriel3562]

As for your first question, some genetic disease require a certain amount of build up before they actually manifest, a good example would be Huntington's disease. The cause is a replication of DNA code which is present from birth, and a dominant mutation which means that if you have one copy of the 'wrong' gene you will present with the symptoms, regardless of the presence of a 'normal' gene. However the damage done by the replication of code takes time to build up, so the first symptoms generally don't occur till adulthood. You could be diagnosed with the illness much earlier if you do a DNA test as a 100% of individuals with the gene will become ill. But diagnosis based on symptoms won't be possible till at least 30-35 years of age.

For the second question, familial disorders can be hereditary, and often are: think of the BRCA breast cancer gene. This is hereditary and (therefor) occurs often in one family. But not all familial disorders can be traced back to a single gene. Some familial disorders are caused by a combination of genes, or even a combination of genes and lifestyle. The genes themselves would also be hereditary, but given that a particular combination is needed presentation of the disease might not follow the typical Mendelian patterns. Having said that, when medical professionals start using the term 'familial' they often tend to use it to describe diseases that have at least a partially defined (genetic) cause. For example familial hypercholesterolemia which is caused (in most cases) by an LDL receptor mutation, but perhaps an individual with one of the milder mutations and a very healthy life style might not suffer from hypercholesterolemia, or at least doesn't have the same build up of plaque as members of his family with a worse mutation and a less healthy life style.

Some congenital diseases can indeed be hereditary/familial, but the presentation of the hereditary or familial disease would need to be present at birth. An example would be cystic fibrosis, a hereditary illness that can manifest (in particularly unlucky cases) at birth. But not all congenital diseases are familial or hereditary, take for example the club foot. This is a congenital condition (present at birth) but not caused by inherited genes from the parents (as far as we know now), in fact the cause of clubfeet is not known yet and hypothesis range from early mild disorders of bone growth to a lack of space in the womb leading to deformed growth.

The last one might depend entirely on what exactly one calls 'familial' if we define the term as an abnormally high occurrence of a defect or disease within a family then we could call cardiovascular disease in a family that has a very unhealthy diet a familial (and acquired) disease. However most often the term familial is reserved for illness that have at least some genetic basis, and therefore would not be entirely acquired. Unfortunately for a number of familial disease no immediate cause has been found, and in that case the argument can be made that the cause is a combination of acquired and genetic causes. Still in my opinion familial diseases shouldn't be listed under acquired, at least not fully, as a good number of familial disease do have genetic causes.

 

[sameeralord]

@galadriel3562: Thanks a lot for taking your time to answer my question. I really appreciate it. Cleared a lot of grey areas. So in essence from what I read, I think Hereditary problems can be nicely explained by Mendelian patterns, but familial do not in all cases, some they do.

 

[galadriel3562]

@galadriel3562: So in essence from what I read, I think Hereditary problems can be nicely explained by Mendelian patterns, but familial do not in all cases, some they do.

In essence: yes. Though keep in mind that it isn't always so nicely divided as we might like, there's exceptions to any rule...for example, here's a whole table of hereditary (genetic) disorders with non-mendelian inheritance patterns...http://hmg.oxfordjournals.org/content/13/suppl_2/R225/T1.expansion.html

 

[sameeralord]

Thanks. I see. Also from re reading your previous response. I think all hereditary diseases are also familial, but all familial diseases are not hereditary. Is that a fair assumption?

 

[galadriel3562]

Thanks. I see. Also from re reading your previous response. I think all hereditary diseases are also familial, but all familial diseases are not hereditary. Is that a fair assumption?

Yes, a hereditary disease is almost by definition also familial. But not all familial diseases are hereditary, depending on the mode of transmission for the familial disorder (acquired or genetic, or a combination of both)

 

[Yorgus]

To muddy it a bit more, a genetic disorder might not be inherited; it may have arisen from a spontaneous mutation. I know an individual who has multiple osteochonromatosis, which is associated with EXT1, EXT2 and EXT3, found on chromosomes 8, 11, and 19 respectively; in each case it is an autosomal dominant gene. Like many who have this disorder, this individual has no discernible family history of the disease (from either parent); thus the conclusion that it was a spontaneous mutation. Two of her three daughters also have the condition.

 

[phinds]

Conigenital actually means present FROM birth. That is, it is not just a condition with which someone was born, it is a condition that someone has had ever since they were born and they still have it.