Cryptococcosis in cats: nasal swelling and diagnosis
6-year-old cat with sneezing, nasal discharge and a firm swelling over the bridge of the nose ('Roman nose'), plus two ulcerated nodules on the head. Fine-needle aspirate cytology of a nodule shows round yeasts of variable size surrounded by a thick clear halo, with narrow-based budding.
Which test confirms the diagnosis and also helps monitor response to treatment?
chevron_right Show answer and explanation
A. Leishmania PCR on the biopsy
Leishmania amastigotes are much smaller (2–4 µm), lie within macrophages and have no capsule. The description is typical of Cryptococcus.
B. Fungal culture for dermatophytes on DTM
Dermatophytes infect hair and the stratum corneum and do not form nodules with encapsulated yeasts; DTM is not the medium for systemic fungi.
C. Serology for antibodies against Cryptococcus
Antibody detection is not used in practice: what is measured is the capsular antigen, whose concentration reflects the fungal burden.
D. Detection of capsular antigen in serum (latex agglutination or lateral flow assay)
Correct. Cryptococcal capsular antigen testing is sensitive and specific. The titre is repeated during antifungal treatment (fluconazole or itraconazole, for months), which continues until the antigen becomes negative.
lightbulb Key takeaway
Cryptococcosis is the most common systemic mycosis in cats. It is acquired from the environment (pigeon droppings, eucalyptus trees), not by direct contagion. Suspect it with nasal swelling, skin nodules on the head or neurological or ocular signs, and look for the capsule halo on cytology.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.