Glucocorticoid excess: This is the most likely cause of severe eosinopenia. Glucocorticoids are known to suppress the production and release of eosinophils from the bone marrow, leading to eosinopenia. The normal tryptase and serum levels support this diagnosis, as glucocorticoid excess does not typically affect these parameters.

Severe bacterial infections: Certain severe bacterial infections, such as sepsis, can cause eosinopenia due to the body's stress response and the release of cortisol. Normal tryptase and serum levels do not rule out this possibility.
Chronic stress: Chronic stress can lead to increased cortisol production, which in turn can cause eosinopenia. This diagnosis is plausible given the normal tryptase and serum levels.
Hypersplenism: Hypersplenism can lead to sequestration of eosinophils in the spleen, resulting in eosinopenia. However, this diagnosis may be less likely given the normal serum levels.

Adrenal crisis: Although less likely, adrenal crisis (e.g., Addisonian crisis) can present with eosinopenia due to the sudden loss of cortisol production. It is crucial to consider this diagnosis, as it is life-threatening if missed.
Sepsis with adrenal insufficiency: This condition can present with eosinopenia and normal tryptase and serum levels. It is essential to rule out sepsis, especially in critically ill patients, as it can be fatal if not promptly treated.

Myeloproliferative neoplasms: Certain myeloproliferative neoplasms, such as chronic myeloid leukemia, can cause eosinopenia. However, these conditions often present with other abnormalities in the complete blood count and are less likely given the normal tryptase and serum levels.
Lymphoma: Some types of lymphoma can cause eosinopenia, although this is a rare presentation. Normal tryptase and serum levels do not rule out this possibility, but it is less likely than other diagnoses.