Go through information of other diseases that a similar to the one you are researching on and see if you will not get relevant information that can be an answer to your research questions

Try google for any help and search information using some of the key words that you feel are related to your questions in mind that need anwers

Good luck

Dear virtuous, for the occurrence of such a situation in scientific research, we cite sources close to the specialty, and we mention that for lack of sufficient sources, the researcher resorted to seeking the help of sources close to the sources related to the subject of the research.

This is the central challenge. You are supposed to pick a topic that fits in a gap in the literature, and then are expected to review the literature that is...but there's a gap, isn't there!? What are you supposed to write about?

So, there are a couple of approaches you can use. And you can use both of them in the same lit review.

1) However big the gap is, there is a perimeter around the gap. How close can you get?

In your case, what about people with other diseases? You then need to pick the most salient aspects of your disease(s) in question and find others who share those points. Not that this is my field, but here are some aspects to consider:

* Curability?

* Existence of treatment?

* Similarly of symptoms?

* Similarity of underlying mechanisms?

* Prognosis for survival (for how long?)

* Side effects of treatments?

* Contagiousness?

* Genetically linked?

This entails anticipating the kinds of issues that you are going to be looking into in your data collection and analysis. What might be relevant, that it might help you to be more informed and reading when developing your instrument (e.g., interview guide), when doing through data collection (e.g., the kinds of things you listen for an follow up about in your semi-structured interviews) and when doing your data analysis (e.g., what threads to look for when coding).

It is a mistake to think that the literature review is done before you've collected data. You can during during data collection and/or analysis that there's a theme in there that you didn't anticipate. You should go back to the literature to find out what others might have found about that in other disease contexts. Then, your final literature review is different than your original literature review. The lit review should inform the study and inform the reader. If there is stuff in there that did NOT arise in your data or findings, you should address that in your Discussion. If there's stuff in your data or findings that was not in your original lit review, you should go back see if you can find other stuff that might help you to better understand it.

It's iterative. It's always iterative.

2) Don't forget methodology. Even if the other diseases or conditions themselves are different, you can look at the approach and instruments used by others. You an look at the sampling strategies. You can look at the analytical approaches. You can do this to inform your methodology section, but you can also do this for your lit review. And you certainly can look at very different approaches to more similar diseases (e.g., quant vs. qual).

Great question! I suggest adding references to the Quality of Life with each specific disease independently and looking for resources that highlight QoL challenges for individuals with comorbid diseases. This helps draw the parallels to your work and allows you to highlight the gaps in the literature regarding QoL for those with comorbidity of the diseases you are studying. I hope this helps!

Your research must have related literature, if not then you won't have theoretical framework, good research questions and objectives. Thus I advise that better change the topic or consult your supervisor. Thanks.

Peruse logically through others people work that similar to your topic, there, you may extract some ideas thereof for your own consumption. Thanks you!

You can start by searching for any available resources on the topic and then evaluate them. You can also consider expanding your search to related topics or fields. If you are still unable to find enough resources, you can discuss the limitations of your literature review in your paper and suggest areas for future research