A 42-year-old man complains of weakness, palpitations, nosebleeds, and skin hemorrhages. His condition progressively deteriorates throughout the last month. Objectively, his condition is severe, he has petechial and spotted hemorrhages on the skin of his limbs and torso, lymph nodes and spleen are not palpable, the pulse is 116 / min., the liver is +2 cm. Complete blood count revels pancytopenia. What disease can be primarily suspected in this case?