Patient, male 4 years old, was admitted because of "some bruise and petechiae had been found for 3 month". The patient was quite well untill his mother found that this cruras appeared some petechiae and bruise without an inducement. About 1 week ago, the patient got a fever after "caught a cold" and then was found that the number of the petechiae incresed and the condition become more serious with pale facial appearance, inertial. Until the patient wwas admitted, no haematemesis and hematochezia was found. The stool and urinating was normal. Physical Examination: T:37.5 degree celsius, P:100/min R:26/min, the petechiae can be found in whole body. The lymphocytes is not palpable. The rest was normal.Blood Figure:WBC 2.2*10^9/LGr 0.123LY 0.847MO 0.030RBC 2.4*10^12/LHb 71g/LRet 0.1%Plt 25*10^9/L Can you explain why this boy have those symptoms and signs. And can you point out what is the main problem for this boy's blood hemogram?