What bone diseases are caused by an epidermis being a completely effective barrier to uv rays?

Rickets. The classic answer is rickets, which is a disease of bone due to severe vitamin d deficiency caused by low dietary consumption and low sunlight exposure. Historically rickets is a disease that affects darkly pigmented individuals. As other, more subtle functions of vitamin d are being described and sunscreen is more widely used, vitamin d levels below recommended levels are becoming more common.