Case study edited by Phil Tucak.
Major Tom is a two-year old exotic shorthair cat who presented to the Small Animal Specialist Hospital (SASH) in Sydney in July 2019 for investigation of progressive right exophthalmos, bilateral mucopurulent ocular discharge and sneezing of six months duration. Major Tom had recurrence of corneal ulceration and recently, he developed a poor appetite and gradual weight loss. A prior treatment trial had included anti-inflammatories (meloxicam 0.1mg/kg SC) and antibiotics (doxycycline 5mg/kg PO twice daily) which made no difference to his clinical signs.
On the first day at SASH, Major Tom’s general physical examination was unremarkable. Ophthalmic examination revealed multiple abnormalities of the right eye. There was moderate conjunctival hyperaemia, marked exophthalmos, absence of menace response and poor direct pupillary light reflex. Major Tom had concurrent entropion and trichiasis which were thought to be breed-related. He had mild uveitis in the right eye. The right cornea had a horizontal band (5mm) of pale sequestrum and mild oedema over its dorsotemporal region with associated neovascularisation.
A complete blood count and biochemistry were unremarkable except for mild azotaemia 211 (71-212 umol/L). The Cryptococcal Antigen Lateral Flow Assay was negative.
To further assess the cause of exophthalmos, a CT scan of the skull was performed. The CT revealed a retrobulbar mass adjacent to the orbital lamella of the right maxilla with possible intranasal extension. This mass was even more obvious after contrast administration. The centre of the mass remained poorly enhanced which is most consistent with necrosis. Major Tom’s cribriform plate was intact and there was no evidence of intracalvarial extension. CT scans of the thorax and abdomen were reported to be normal. The two main considerations for these changes were infiltrative neoplastic disease (e.g. lymphoma) or infectious disease (bacterial or fungal disease). Our surgery team was able to obtain a retrobulbar mass biopsy via an intraoral approach. A temporary tarsorrhaphy was performed at the same time to protect the cornea from further injury. Histopathology of the retrobulbar mass revealed severe necrotising, eosinophilic and granulomatous cellulitis with numerous fungal hyphae present. Anaerobic and aerobic culture grew Bergeyella zoohelcum which we consider to be an oral contaminant. Aspergillus species was isolated from the retrobulbar tissue.
Major Tom was diagnosed with sino-orbital aspergillosis. There are two forms of upper respiratory tract aspergillosis (URTA): sino-orbital (infection extends from the nasal cavity to paranasal structures, including the orbit) and sino-nasal (infection remains confined to the sino-nasal cavity). Both infections start in the nasal cavity and brachycephalic breeds of cats are predisposed to URTA. Sino-orbital aspergillosis is usually caused by Aspergillus Felis, however molecular identification is required to differentiate Aspergillus Felis from other forms of Aspergillus species. Further comparative sequence analysis and anti-fungal susceptibility were not performed in this case.
Sino-orbital aspergillosis generally carries a poor prognosis. A standard treatment protocol has not been established. Successful treatment with itraconazole or posaconazole either alone or in combination with amphotericin B, or topical therapy with intranasal clotrimazole have been previously reported. For Major Tom, we commenced posaconazole (30mg/kg PO first dose then 15mg/kg PO q48h) combined with amphotericin B (AMB).
Amphotericin B deoxycholate (Fungizone 50mg vial) was given as a continuous rate infusion over five days with intravenous fluid therapy. We were hoping to achieve 0.5mg/kg/24 hours to reach an accumulative maximum dose of 16mg/kg. During the AMB treatment, there was no renal tubular cast noted on daily urine sediment examination. Major Tom’s creatinine remained stable at 205umol/L (71-212umol/L) on Day 5.
Major Tom’s corneal ulceration and uveitis were treated with ofloxacin (topical q6h) and chloramphenicol ointment (topical q6h). He received an appetite stimulant (mirtazapine 1.875mg PO every second day) and pain relief (buprenorphine 0.02mg/kg trans-mucosally three times daily).
Over the next two weeks, Major Tom was clinically well and his appetite returned to normal. His exophthalmos was still present but slightly improved from the previous visit. Due to the risk of worsening kidney function in a young cat, we elected to discontinue Major Tom’s AMB treatment. He will likely stay on his posaconazole treatment for life.
Major Tom made remarkable improvement over the following months. In September, his right corneal sequestrum appeared to have resolved completely. Corneal oedema and ulceration were much improved. There was a dense horizontal band of slightly raised vascularisation in the middle. Although the right eye did not appear to be visual it was comfortable.
In October 2019, Major Tom had minimal exophthalmos and his corneal ulceration was resolved. He had occasional sneezing with nasal discharge. The owner reported excellent progress. Due to permanent visual loss of the right eye and poor corneal or eyelid sensation, Major Tom presented to us again in December for evaluation of multiple corneal ulcerations. We have recommended a semi-permanent tarsorrhaphy to help protect his cornea. The surgery was uneventful and Major Tom continues to do well.
Dr Joyce Chow BVSc MANZCVS
Dr Joyce Chow is a medicine resident at the Small Animal Specialist Hospital (SASH) in Sydney.
Dr Chow spent three years in small animal practice in Canberra before joining SASH in 2016 where she completed a rotating internship.
Dr Chow is interested in all areas of internal medicine, particularly gastrointestinal and liver diseases.
She worked closely with Dr Amy Lam to treat Major Tom’s sino-orbital aspergillosis.