Welp... I think things are even more depressing than we thought.
So, the Sapphire Scale disease was contracted to Bonney by Ginny. We know Ginny died long before Bonney was born, and that Bonney developed the disease five years after Ginny's death.
This means the disease was something Ginny received from the Celestial Dragons that was genetic, and spread down to Bonney.
The Saphire Scale disease causes the people exposed to it to have their skin turn into blue scales when exposed to any natural light. So, in order to protect yourself from it, you'd need something to shield you from light at all times. While it is said to be incurable, we know from Hiriluk that there's no such think as incurable disease, and if the Celestial Dragons had that disease themselves, why isn't it spreading among them, like with Ginny? Also, the disease should be killing them if they get it, so they must have some kind of cure. Furthermore, Bonney no longer has the disease, proving that there is some form of a cure.
Through history, royalty has been known for incest and rape, with many royals marrying close and distant family to preserve their line, and yielding illegitimate children with the peasantry. Because of this, royalty through history, like the Celestial Dragons, have come to develop a high rate of sexual mutation and spread of STDs.
Like I said, the Sapphire Scale disease is spread through contact to light. What are the Celestial Dragons wearing? Airtight suits with helmets. But, some, like Garling, do not have these suits. I believe the CDs with suits are the more inbred type, who've contracted the Sapphire Scale disease through inbreeding and horrible sexual health/morality, like Charlos.
This is why Garling has no problem walking around without a suit, he doesn't have the Sapphire Scale Disease. Vegapunk is working for them to outright try to find a cure for it.
This is a really sad option, because it would mean Ginny's rape also directly led to her death. There's a possibility the Sapphire Scale disease is an STD, sadly.