Final answer:
The most likely diagnosis for the patient's symptoms and enzyme deficiency is Gaucher disease, and the treatment is enzyme replacement therapy.
Step-by-step explanation:
The most likely diagnosis for a 20-year-old male who presents with anemia, hepatomegaly, splenomegaly, thrombocytopenia, nosebleed, and bruising, along with a deficiency of glucocerebrosidase enzyme revealed in a test of peripheral leukocytes, is Gaucher disease. Gaucher disease is a genetic disorder resulting from the lack of glucocerebrosidase enzyme, which is necessary for the breakdown of glucocerebroside, a lipid that can accumulate in organs and bone marrow if not properly metabolized, leading to the symptoms observed.
The recommended treatment for Gaucher disease is enzyme replacement therapy, which involves periodic infusions of the deficient enzyme to help reduce lipid accumulation and alleviate symptoms.