Tirdeck’s disease

This disease causes the victim's bones to slowly melt, causing disfigurement followed by death.

Transmission & Vectors

Spread by touch, victims are infectious from approximately 2 weeks after catching it.  They remain infectious until cured.  The disease is remarkably resilient and can survive in a body for several weeks after death.

Causes

For centuries the source of this disease was unknown. With a high infection and nearly 100% mortality rate it could destroy a village but after everyone was dead it would have no way to spread. Still somehow it would reappear with no reasonable explanation. It was finally a cleric who was treating an afflicted village who discovered the source. The disease was caused by interacting with demons. This revelation led to the disease gaining a new stigma, with the first person to be diagnosed often being stoned to death by their neighbours.  This has led to people frequently trying to conceal their symptoms which allows the disease to spread through a community.

Symptoms

Symptoms begin to appear about a week after infection with the first sign usually being difficulty in picking things up. The next symptom is pain in the feet followed by an inability to walk as the bones in the feet soften. The bones in the hands are the next to soften into uselessness, followed by the limbs. The spine starts to soften followed by the rib cage and finally the skull.
The speed with which symptoms appear varies from person to person.  Unlike many other diseases the fitter and stronger someone is the faster they will succumb.  This is because the stronger the muscles are the easier it is for them to bend or break the weakened bones.

Treatment

Divine healing can halt the progress of the disease, though clerical healers do have to take precautions to avoid getting infected themselves.  During the third age a blend of healing herbs was also found to be effective if administered in an area that was sanctified.  Neither method restores the bones to their former condition, nor do they prevent the victim catching the disease again.
Only powerful healing magic, of the sort that can regrow lost limbs, is capable of restoring the bones.  This can be a long and painful process depending on how far the disease had progressed.

During the Second Age investigating outbreaks of this disease was assigned to members of the Order of the Shield. These holy warriors were dispatched to identify and eliminate the source of the disease before trying to treat the afflicted.  While a logical approach, the knights gained a reputation for being more concerned with punishing evildoers than saving the victims of the disease.