Right antebrachial swelling and lameness in a 1.5-year-old intact female German Shepherd Dog

Kaitlin Thorp
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Steven Robillard
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 DVM, DACVR
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Alisa Berg Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL

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Autumn Harris
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 DVM, DACVIM, PhD
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Federico R. Vilaplana Grosso
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 LV, DECVDI, DACVR

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History

A 1.5-year-old 24-kg intact female German Shepherd Dog presented to the primary veterinarian for a history of lameness and swelling on the lateral aspect of the right antebrachium. The dog was initially administered a tapering anti-inflammatory course of prednisone and oclacitinib (1 mg/kg orally, per day) for suspected allergic dermatitis based on licking the right forelimb. Approximately 3 weeks later, the patient developed generalized seizures, which progressed to unyielding cluster seizures. The dog was then referred to the University of Florida Small Animal Hospital, by which point the patient was post-ictal, laterally recumbent, and minimally responsive. Neurologic examination revealed stuporous mentation, miotic pupils, nonambulatory tetra-ataxia, delayed postural reactions, and cranial nerve deficits (absent menace in the right eye and decreased gag reflex). Overall, neurolocalization was multifocal to left-sided forebrain disease. In addition, a firm, painful swelling was palpated on the distolateral aspect of the right antebrachium. The remainder of the physical examination was unremarkable. A vector-borne screening test (SNAP 4Dx; IDEXX) was performed, which was negative for heartworm, Lyme disease, Ehrlichia, and Anaplasma. A CBC revealed a mild leukocytosis (20.5 K/μL; reference range, 4.6 to 11.6 K/μL) characterized by a moderate neutrophilia (13.0 K/μL; reference range, 2.6 to 8.0 K/μL) with mild left shift (210 bands, no toxicity), mild monocytosis (2.1 K/μL; reference range, 0.1 to 0.9 K/μL), mild eosinophilia (2.9 K/μL; reference range, 0.1 to 1.7 K/μL), and mild basophilia (0.41 K/μL; reference range, 0 to 0.1 K/μL). A chemistry panel was performed, yielding mildly elevated AST (60 U/L; reference range, 16 to 53 U/L), ALT (105 U/L; reference range, 23 to 93 U/L), ALP (144 U/L; reference range, 7 to 166 U/L), sodium (152.9 mmol/L; reference range, 141.9 to 150.6 mmol/L), and potassium (6.2 mg/dL; reference range, 2.2 to 4.8 mg/dL). Orthogonal radiographs of the right antebrachium (Figure 1) were obtained.

Figure 1
Figure 1

Mediolateral (A) and craniocaudal (B) radiographic images of the right antebrachium of a 1.5-year-old 24-kg spayed female German Shepherd Dog presenting for progressive seizures and a swelling on the lateral aspect of the thoracic limb.

Citation: Journal of the American Veterinary Medical Association 262, 4; 10.2460/javma.23.12.0667

Diagnostic Imaging Findings and Interpretation

Right antebrachial radiographs revealed a monostotic aggressive bone lesion centered in the distal diaphysis of the ulna, characterized by an amorphous, continuous, irregularly marginated, and ill-defined periosteal reaction surrounding the distal ulna; moth-eaten lysis with cortical destruction; and a long and ill-defined zone of transition, with associated moderate focal soft-tissue thickening (Figure 2). Considering the patient age, breed and multifocal clinical presentation, the primary differential diagnosis was infectious osteomyelitis (fungal Aspergillus spp were considered most likely due to the patient signalment) with suspicion of disseminated infection. Primary osseous neoplasia such as osteosarcoma, or bone metastasis were considered less likely. Thoracic radiographs were performed to evaluate for further evidence of disseminated infection (eg, intrathoracic lymphadenopathy, bronchopneumonia, discospondylitis) or evidence of metastasis.

Figure 2
Figure 2

Same radiographic images as Figure 1. A well-defined, mixed expansile, and moth-eaten osteolytic lesion is centered on the distal diaphyseal region of the right ulna. The lesion is characterized by continuous, irregular periosteal proliferation, a long and ill-defined zone of transition. There is moderate focal overlying soft-tissue swelling.

Citation: Journal of the American Veterinary Medical Association 262, 4; 10.2460/javma.23.12.0667

Three-view thoracic radiographs revealed a relatively well-defined, irregularly marginated, rounded, expansile osseous mass on the distal aspect of the left third rib, measuring approximately 2.8 X 3 cm (Figure 3). The lesion appeared to be extending into or centered within the costochondral junction. No other osseous lesions were noted, and the pulmonary parenchyma, cardiovascular structures, and remaining intrathoracic structures were unremarkable. The primary differential diagnosis for this osteoproliferative osseous lesion in the left third rib in conjunction with the right antebrachial aggressive bone lesion was fungal osteomyelitis, and was consistent with the initial diagnostic suspicion after the antebrachial radiographs. Primary osseous neoplasia such as osteosarcoma, or bone metastasis were again considered less likely.

Figure 3
Figure 3
Figure 3
Figure 3

Right lateral (A), left lateral (B), and ventrodorsal (C) thoracic radiographic images of a 1.5-year-old 24-kg spayed female German Shepherd Dog presenting for progressive seizures. A focal, ovoid, smoothly margined, well-defined mineral-opaque mass is present in association with the ventral aspect of the left third rib (arrowheads), extending into the costochondral junction. The lesion is not definitively identified on the orthogonal ventrodorsal projection; however, laterality can be inferred from differential magnification and following the margins of the ribs on the right/left lateral images.

Citation: Journal of the American Veterinary Medical Association 262, 4; 10.2460/javma.23.12.0667

Focal ultrasound examinations of the distal right antebrachium and left third rib were performed to obtain fine needle aspirate samples of the identified lesions (Figure 4). The right ulnar lesion appeared as an irregular, hypoechoic expansion of the bone with multifocal cortical discontinuity. The rib showed extensive irregular osseous proliferation and numerous regions of cortical discontinuity.

Figure 4
Figure 4
Figure 4

Transverse (A) and longitudinal (B) ultrasound images of the left distal antebrachium and left third rib, respectively. A—There is severely irregular cortical disruption and bony irregularities affecting the distal ulna, with thickening of the antebrachial soft tissues (asterisk). B—(Proximal is to the right) there is an irregular, expansile, strongly shadowing lesion confluent with the ventral portion of the left third rib (asterisk). White arrowheads indicate the margins of the normal part of the rib.

Citation: Journal of the American Veterinary Medical Association 262, 4; 10.2460/javma.23.12.0667

Treatment and Outcome

Cytology of both the right ulnar and the left third rib lesion showed marked pyogranulomatous inflammation with intralesional fungal hyphae, and for further speciation, an Aspergillus enzyme immunoassay Galactomannan Serum Antigen test (Miravista) was submitted, yielding a positive 9.45 index, as well as Aspergillus Galactomannan Urine Antigen test (Miravista), which resulted in a positive 6.54 index. Panfungal PCR sequencing (Molecular Fungal ID Lab; University of Florida) of osseous lesion cytology was consistent with phaeohyphomycosis, isolating DNA sequences matching Phaeoacremonium spp with 98.77% and 99.2% identity when analyzed with the National Center for Biotechnology Information (NCBI) Basic Local Alignment Search Tool (BLAST) database. As Galactomannan positivity is not specific to Aspergillus spp, primary disseminated phaeohyphomycosis was prioritized and the patient was started on voriconazole (4 mg/kg, PO, q 12 h), prednisone (0.5 mg/kg, PO, q 24 h for 5 days, then 0.25 mg/kg, PO, q 24 h for 5 days, 0.25 mg/kg q 48 h until complete), levetiracetam (60 mg/kg, PO, q 8 h), and phenobarbital (3 mg/kg, PO, q 12 h). After 10 days of hospitalization, the patient was static to mildly improved, and the owner elected to take the dog home; however, the dog re-presented for progressive decline and fever 2 days later and was humanely euthanized. A necropsy was performed, which revealed disseminated systemic mycosis with meningoencephalitis, hepatitis, osteomyelitis (rib and ulna), nephritis, myocarditis, pneumonia, and splenic infarction.

Comments

Localized and disseminated fungal infection is a semi-commonly recognized entity affecting humans, wildlife, and domestic animals such as dogs and cats.1,2 In the dog, certain breeds (eg, German Shepherd Dog) and body morphologies (doliocephalic) have been associated with increased incidence of fungal infection. In regards to disseminated infection, a heritable immunoglobulin A deficiency has been identified in German Shepherd Dogs and has been linked to opportunistic infection by certain fungal species (most commonly Aspergillus spp).3 Disseminated fungal infection may affect any organ but is most frequently reported to cause discospondylitis, osteomyelitis, meningoencephalomyelitis, pyonephrosis, splenitis, lymphadenitis, and hepatitis.2

Phaeoacremonium is a genus of opportunistic fungal plant pathogens and endophytes from the dematiaceous group.4,5 They infect woody plants and are known to cause a well-recognized disease of grapevines called Petri disease. In humans, Phaeacremonium infections are mostly reported to be traumatically inoculated and result in subcutaneous abscesses or mycotic arthritis (no cutaneous lesions were identified in our case); however, osteomyelitis, endocarditis and disseminated infections have been documented.5 To the author’s knowledge, this is the first description of a disseminated phaeacromonium infection in a dog.

In this case, performing thoracic radiographs after the antebrachial study allowed for the identification of polyostotic aggressive lesions (antebrachium, rib) which assisted in prioritization of differential diagnoses. This is because noting a solitary monostotic aggressive bone lesion (particularly in the distal antebrachium) may have led to the incorrect prioritization of neoplasia such as osteosarcoma, as the radiographic appearance of fungal osteomyelitis shares considerable overlap with that of osseous neoplasia (eg, cortical/medullary lysis and periosteal proliferation). Osteosarcoma, in particular, has a bimodal age distribution and predilection for the distal antebrachium and large and giant breed dogs.

Additional radiographic features of disseminated fungal infection that could (but were not) identified on thoracic radiographs in this case that would help to discriminate the diagnosis from neoplasia include lysis/proliferation centered on the intervertebral disc space (discospondylitis) and intersternebral cartilages, tracheobronchial and/or cranial mediastinal lymphadenopathy, bronchopneumonia, myocarditis (cardiomegaly), or hepatitis (hepatomegaly).1,2

In this case, the use of ultrasound facilitated image-guided tissue sampling of both the antebrachial and rib lesions to obtain a diagnosis. In retrospect, additional imaging of the patient would have been useful in qualifying this rare fungal infection more clearly. For example, an abdominal ultrasound may have been useful in determining the degree of organ involvement. Findings such as hepatic and splenic changes (enlargement, masses, heterogeneity), lymphadenopathy, and hypoechoic material in the renal pelvis (eg, pyonephrosis) might have been identified, considering the necropsy findings.5 In addition, given the presence of seizures, an MRI of the brain may have good diagnostic value.

Ultimately, this case highlights the importance of synthesizing diagnostic imaging findings in combination with the patient signalment and clinical history. The proper parallel interpretation of these methods of diagnostic information facilitated the rapid diagnosis and initiation of antifungal therapy, maximizing the chance of a positive clinical outcome.

Acknowledgments

None reported.

Disclosures

The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.

Funding

The authors have nothing to disclose.

References

  • 1.

    Ettinger SJ, Feldman EC. Textbook of Veterinary Internal Medicine. Elsevier; 2004:996-1002.

  • 2.

    Schultz RM, Johnson EG, Wisner ER, Brown NA, Byrne BA, Sykes JE. Clinicopathologic and diagnostic imaging characteristics of systemic aspergillosis in 30 dogs. J Vet Intern Med. 2008;22(4):851-859. doi:10.1111/j.1939-1676.2008.0125.x

    • Search Google Scholar
    • Export Citation
  • 3.

    Day MJ, Eger CE, Shaw SE, Penhale WJ. Immunologic study of systemic aspergillosis in German Shepherd Dogs. Vet Immunol Immunopathol. 1985;9(4):335-347. doi:10.1016/0165-2427(85)90063-7

    • Search Google Scholar
    • Export Citation
  • 4.

    Rodriguez-Materon S, Trynz S, SanGiovanni TP. Fungal osteomyelitis due to Phaeoacremonium venezuelense: a case report. JBJS Case Connect. 2022;12(2):e22.00083. doi:10.2106/JBJS.CC.22.00083

    • Search Google Scholar
    • Export Citation
  • 5.

    Wong PK, Ching WT, Kwon-Chung KJ, Meyer RD. Disseminated Phialophora parasitica infection in humans: case report and review. Rev Infect Dis. 1989;11(5):770-775. doi:10.1093/clinids/11.5.770

    • Search Google Scholar
    • Export Citation
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