According to the text, what specific medical condition did the nephew of the Malegaon doctor have, and why was it considered so severe?

The source material from Chapter 34 identifies the ailment as a bone-cyst, referred to by the name Hadyavran. It was deemed an extraordinarily severe and difficult malady because it was completely unresponsive to treatment. The text emphasizes that the boy's uncle was a degree-holding doctor who, along with his physician friends and even expert surgeons, had tried all available native and foreign treatments. Even a surgical attempt failed, leaving them exhausted and helpless. This complete failure of medical science to provide any relief is what characterized the severity of the illness and caused the young patient immense pain and suffering.