To be absolutely true here, this is a worldwide issue, of not being able to diagnose medical problems, because a persons skin is “dark”. Most diseases are studied on white, or light skinned people, and shamefully, there are almost no pictorial examples of the same diseases on Black skin. And no will or need for most of the medical professions to fix it!
There was a Black doctor who had to start a pictorial dictionary of different skin conditions on dark skin. That’s how bad this is in the medical community. You’ve got entire industries (like tattooing and hairstyling) that don’t know how things look or work on half the planet!