What was the disease that afflicted the nephew of the Malegaon doctor, and why was it considered so severe?

The ailment that afflicted the doctor's nephew is identified in Chapter 34 as a bone-cyst, referred to as Hadyavarn. It was considered an extraordinarily severe and difficult malady because it resisted all forms of treatment. The text explicitly states that the boy's own uncle was a degree-holding doctor, and he, along with his physician friends and even expert surgeons, were helpless. They tried all native and foreign treatments, including surgery, but every effort was exhausted without any success. The severity was marked by the failure of all human expertise and the immense, unbearable pain the young nephew suffered.