Invasive Candidiasis: This condition is characterized by a significant increase in serum beta-D-glucan levels, which is a cell wall component of fungi, including Candida species. Leukocytosis is a common response to invasive fungal infections, making invasive candidiasis a leading consideration given the combination of findings.

Pneumocystis jirovecii Pneumonia (PCP): While more commonly associated with immunocompromised patients, PCP can cause an increase in beta-D-glucan levels due to the fungal nature of the pathogen. Leukocytosis may also be present, especially in severe cases.
Aspergillosis: Similar to invasive candidiasis, aspergillosis can cause elevated beta-D-glucan levels. Leukocytosis is a common finding in invasive aspergillosis, particularly in immunocompromised patients.
Histoplasmosis: This fungal infection can also lead to increased beta-D-glucan levels and leukocytosis, especially in disseminated disease.

Pseudomonas aeruginosa Infection: Although beta-D-glucan is more specific to fungal infections, certain bacterial infections, including Pseudomonas, can cause false-positive elevations in beta-D-glucan due to the presence of beta-D-glucan-like structures in some bacterial cell walls. Leukocytosis is common in severe bacterial infections.
Trichosporonosis: A rare but potentially life-threatening fungal infection that can cause elevated beta-D-glucan levels. It's essential to consider this diagnosis, especially in immunocompromised patients.

Fusariosis: A rare fungal infection that can cause increased beta-D-glucan levels and leukocytosis, particularly in immunocompromised individuals.
Scedosporiosis: Another rare fungal infection that may present with elevated beta-D-glucan levels and leukocytosis, often in patients with compromised immune systems.
Mucormycosis: Although beta-D-glucan levels may not be as consistently elevated as in other fungal infections, mucormycosis is a critical diagnosis to consider due to its high mortality rate, especially in diabetic or immunocompromised patients.