Is there a relation between protein domains and diseases ?

What's your definition of disease?

Many disorders are linked to the misfolding of proteins, such as cystic fibrosis and sickle cell anemia. Albeit, these are congenital anomalies/diseases.

According to my understanding of protein domains, these are the functional parts of the protein. This is where enzymes, for example, catalyze a reaction. When drugs are produced, the chemical interacts with this substrate site to either prevent it from working, or make it work more efficiently.

When the domain is faulty, diseases arise. Proteins are faulty when their domains are not coded correctly, so there is a direct association between these two things. Proteins control almost every aspect in an organisms, so when they fold incorrectly due to defects in the genetic code, things stop working as intended. The genome codes thousands of kinases that perform various task inside cells; if there were a defect in any one of those kinases, the cellular functions would be disrupted without precise regulation.

thank you for the reply both @bio_man and @duddy.
Let me reply here according to what I get from your replies.

As you mentioned, the domain is functional part of protein, and what I found from this image :
ns.png" target="_blank">https://en.wikipedia.org/wiki/Protein_domain#/media/File:Pyruvate_kinase_protein_domai ns.png

is that a protein (in 3D structure) consists of one or more domain(s), and also from the following video:
https://youtu.be/u49k72rUdyc?t=17
It stated that "drug targets are proteins ". As the drug targets some gap (binding site) in the protein which in turn consists of many domains, thus we can claim that this binding site can be related to a domain of those which build up the protein.

Therefore, and based on the first 2 statements of @duddy's answer. if we have this scenario, a malfunction in protein X proven to cause disease Y. Then, all domains that build up the protein X can be a candidate targets for a drug to disease Y, Is that true ?

That's correct. If you can definitely prove that protein x leads to disease y, then targeting that protein is a good start to treatment. Take male pattern baldness as an example. It has been found that people who have the gene that transcribes 5-alpha-reductase are more likely to experience onset baldness. So one way to treat this condition is either reduce the symptoms caused by the presence of this enzyme; for example, increase blood flow to the hair follicles. OR, prevent the enzyme from doing what it does. A visual can be found here: https://learn.ppdictionary.com/offtopic/dht.html

Anyway that sums it up: target domain of a specific protein, you can control what it does.

https://biology-forums.com/index.php?action=gallery;sa=view;id=34396

Lookie here Enzymes can be inhibited at their substrate site (where things get catalyzed, for instance) or from a remote part of the enzyme called the allosteric site. Drugs that target the allosteric site are called allosteric inhibitors. Normally vitamins bind to these sites to make the enzyme run more efficiently