If rare case , why not ?

Dear Nabiha, thanks for sharing your question.

It seems from your description that it was a “case series” in which the authors could describe their experience of a group of patients with similar diagnosis.

That usually happens with rare conditions.

If the occurrence of the event is rare, this can be justified, which is similar to a case series. If the event is not rare, there are several other ways to obtain the sample size