skin issue - red patch

your GP- can then send you to / suggest the appropriate specialist!

or you can randomly pick someone who may or may not be the right one!

Cannot say it enough BELGIUM HAS A MARVELLOUS STATE MEDICAL SYSTEM ! why anyone would want to go private & pay beats me.
Contrary to myth, it's NOT necessary to ask a GP for a referral to a specialist.

UCL Cliniques Universitaires Saint-Luc) is a research & teaching hospital.
Anyone can make an appointment direct with the department you need.
METRO ALMA drops you in the center of the hospital 'village' & follow signs to clinique. address 10 Avenue Hippocrate, 1200 Bruxelles,
Pick up a brochure at reception giving the direct numbers for all departments.
General number telephone is 02-764.11.11
DERMATOLOGIE direct number is 02-762.14.72 to make an appointment.

On your first visit arrive half an hour early with your social security / medical insurance documents / SIS card and get your 'badge' from reception.
The badge links you to the computer, your GP can receive computerised information if you allow it, your Mutuelle will pay their part of the bills automatically. Your medical information, appointments & insurance is all taken care of by the badge which you show at each visit. Marvellous system.

And great medical care - they saved my life & continue to do so.

@parachute
You are quite right when you say that it's not necessary to ask a GP for a referral to a specialist.
HOWEVER, there are many situations where it is best to do so. For example, you will get a higher refund from your mutuelle if you have been referred to a physiotherapist rather than if you have just chosen one at random. What's more, without the prior agreement of your mutuelle, you will only get any refund at all for a limited number of visits to a physiotherapist each year.
In the specific question here, the first respondent suggests a GP visit in order to get a recommendation. Which is better, a GP visit to find out whether you actually need to see a specialist or a specialist visit and a specialist's BILL only to be told that your GP can deal with it.
Finally, your hospital recommendation is great...............for those who live in Brussels. But this is a site for those who live in Belgium rather than just Brussels.

It's true that the OP didn't specify their place of residence and it's true that we shouldn't narrow our thinking down to just Brussels. But the thread is getting a bit too heated for the subject in question, so I suggest being just more understanding...

I've always have had good results with doctor Paul Degardin (he's a skin specialist=dermatolgist) rue Elise in Ixelles (1050)> google him!