Hemolytic Anemia of Newborn (if patient is a newborn): This condition is characterized by anemia, elevated bilirubins due to hemolysis, and can present with leukocytosis as a stress response. The spleen may not be enlarged in early stages or in certain types of hemolytic disease.
Autoimmune Hemolytic Anemia (AIHA): This condition involves antibodies against the patient's own red blood cells, leading to hemolysis, anemia, elevated bilirubins, and sometimes leukocytosis. The spleen size can be normal, especially if the disease is not severe.

Sickle Cell Disease with Acute Crisis: Although sickle cell disease often presents with splenomegaly in children, in adults, the spleen can be small or not palpable due to repeated infarctions (autosplenectomy). An acute crisis can cause anemia, leukocytosis, and elevated bilirubins.
Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency: This enzyme deficiency can lead to hemolytic anemia under certain conditions (e.g., infection, certain medications, or foods). It presents with anemia, elevated bilirubins, and can have leukocytosis. The spleen size is usually normal.
Infections (e.g., Sepsis): Certain infections can cause hemolysis, anemia, leukocytosis, and elevated bilirubins. The spleen size may remain normal, especially early in the course of the infection.

Malaria: Although more commonly associated with splenomegaly, in early stages or with certain species (like Plasmodium vivax), the spleen might not be enlarged. Malaria causes hemolysis, anemia, and can present with leukocytosis and elevated bilirubins.
Babesiosis: This parasitic infection can cause hemolytic anemia, elevated bilirubins, and leukocytosis. The spleen may not be enlarged, especially in asymptomatic carriers or early in the disease.
Severe Combined Immunodeficiency (SCID) with Infection: While not directly causing hemolysis, severe infections in SCID patients can lead to a complex presentation including anemia, leukocytosis, and elevated bilirubins due to liver involvement or hemophagocytosis.

Paroxysmal Nocturnal Hemoglobinuria (PNH): A rare, acquired, life-threatening disease of the blood characterized by the destruction of red blood cells (hemolysis), bone marrow failure, and the potential for blood clot formation (thrombosis). It can present with anemia, elevated bilirubins, and sometimes leukocytosis, with a normal spleen size.
Wilson's Disease: A genetic disorder that leads to copper accumulation in the body, primarily affecting the liver and brain. It can cause hemolytic anemia, elevated bilirubins, and sometimes leukocytosis. Although liver disease is prominent, the spleen may not be enlarged in early stages.