What is the term for the failure of the spleen to develop?

The term for the failure of the spleen to develop is aplasia. Aplasia refers to a condition in which an organ or tissue fails to develop or is absent from birth, representing a complete lack of formation. This condition can result in the absence of the spleen, leading to potential complications related to immune function and hematopoiesis, as the spleen plays an important role in filtering blood and managing the immune response.

In contrast, hypertrophy refers to the increase in size of an organ or tissue due to the enlargement of its cells, not a failure of development. Hypoplasia is a related term that describes underdevelopment or incomplete development of an organ or tissue, meaning the organ is present but is smaller than normal. Meanwhile, atrophy is a condition involving the reduction in size or wasting away of an organ or tissue due to a decrease in cell size or number, which generally occurs after the organ has been fully developed and does not pertain to a failure of development from the start.