Are congenital diseases necessarily hereditary diseases?

Recently I saw someone asking if they should get married because their partner has short fourth metatarsal bone. Today I want to talk to you about this disease.

This article is divided into two parts. The first part is an introduction to the disease, and the second part is some personal views on misunderstandings about the disease.

01. About this disease

First of all, this disease has three characteristics:

1. Incidence.

The incidence of congenital metatarsalgia is about 0.02%-0.05%, which is 0.2 to 0.5 per 10,000 people. How high is this incidence? Let's make a comparison and take a look.

The incidence of colds is about 100%, the incidence of chronic kidney disease is 10.8%, and the incidence of cancer is about 0.2%, or 20 per 10,000.

2. This disease is hereditary. However, the heritability has not been clearly determined. And the exact gene has not been located. Especially for the uncommon condition of short fourth metatarsal (different people have found different possible genes, so it is even more uncertain).

Generally speaking, if the patient has a family history of the disease, such as her parents, grandparents or grandparents have similar symptoms, you can assume that she has the genetic susceptibility to the disease.

3. This disease is more susceptible to females. The general male-to-female ratio is 1:25.

02. Some information about diseases

Regarding diseases, I think there are a few points that must be made clear:

1. Distinguish between congenital and acquired characteristics.

Generally speaking, congenital diseases refer to diseases that are born with the individual, which often involve problems with the genes themselves (but this is not necessarily the case. For example, influences during pregnancy can also cause so-called congenital diseases, but they have nothing to do with genetics), while acquired diseases refer to factors caused by many external factors.

But it is often difficult to distinguish. For example, there is this type of color blindness. Some children are not born color blind, but are affected after birth. By the time they are able to express their feelings, they are already color blind. So some people speculate that they are congenitally color blind, which is wrong.

2. Congenital does not mean hereditary.

The vast majority of traits are not inherited because of gene recombination and exchange in biology, which are the laws we learned in high school.

For example, most of your physical conditions are innate, but not hereditary. Simply put, if you are a boy, you will lose at least half of your innate traits if you give birth to a girl. In other words, inborn ≠ genetic**.

3. The vast majority of diseases are not genetic diseases.

This is also a misunderstanding for many people. Many people think that congenital diseases are genetic diseases. In fact, the genetic diseases we are talking about generally refer to diseases that conform to Mendel's laws, which can generally be described by the Aa, dominant and recessive laws of high school biology.

There is actually a list of these diseases. Most of the diseases we see in daily life do not fall into this category because genes themselves involve several concepts.

03. About Genetics

In addition, in Mendelian inheritance, there are three important terms that can drive you crazy in any minute.

The first one is called penetrance, which has been explained. For example, the night gave you black eyes, but you used them to roll your eyes (the ratio of having a certain gene and the corresponding phenotype).

The second is called pleiotropy: one gene affects multiple traits, for example, a chef who loves to drive is not a good tailor.

The third one is called expressivity: the genes are the same but the traits are different, and you both have great power, but others go to Peking University while you go to Peking University Jade Bird.

Finally, no one is perfect, really. If you don’t believe it, take a whole genome test and you will collapse in minutes. However, everyone has their own choice, which is personal freedom, so I think:

If you can accept it, then go ahead with it;

If it's hard to accept, just let it go.