Blood is very important for the survival and performance of our organs. Blood disorders will affect the balance of our body's organs. Blood consists of several components. There are red blood cells, white blood cells, platelets, and blood plasma.
Called blood disorders if any one or more of these blood components are abnormal, can be excess or lack of numbers, deformities, and disorders of its constituent proteins. For example, a deficiency of red blood cells is called anemia. In platelet deficiency is called thrombocytopenia.
They are "signs" of an underlying disease. Causes of blood disorders can vary, for example there was initially infection, bleeding, immune system disorders, there is interference in an organ such as bone marrow, and lack of nutrients. Because the information you provided does not include the results of a doctor's examination, I can not expect for the exact cause.
To know the exact cause, it must be through physical examination by the doctor and investigation such as complete blood test, blood cell analysis, X-ray if there is marks of enlargement organs, examination of signs of immunity, up to spinal cord if necessary.
All you can do now is support his recovery by strengthening it emotionally and praying for his recovery. So, may be useful yes.