Primary pyomyositis and uveitis in a cat

Abstract

A 6‐year‐old neutered male Siamese cat was referred for investigation of hindlimb ataxia and blindness of 2 weeks’ duration. A swollen right hind limb, with no history of trauma, and no evidence of an external wound, was observed on physical examination. Ophthalmic examination revealed bilateral absence of the menace response and changes consistent with uveitis. Blood tests identified changes consistent with inflammation including serum amyloid A elevation. Infectious disease testing was negative. Degenerate neutrophils and bacterial cocci were detected on fine needle aspiration cytology of the affected limb. Thoracic radiography and abdominal ultrasonography identified no abnormalities. Primary pyomyositis was suspected and clindamycin was prescribed following Penrose drain tube placement. In addition, eye drops containing tobramycin, atropine, and prednisolone were administered. The clinical signs and serum amyloid A level were markedly improved after 5 days of treatment. Based on the medical history and lack of other findings, the uveitis was suspected to be secondary to the pyomyositis. The clinical signs resolved completely, and no recurrence was reported within a 6‐month follow‐up period. To the best of our knowledge, primary pyomyositis with uveitis has not been previously reported in cats.

A 6‐year‐old neutered male Siamese cat was referred for investigation of hindlimb ataxia and blindness of 2 weeks’ duration. Primary pyomyositis was suspected; therefore, clindamycin was prescribed following Penrose drain tube fixation, and eye drops containing tobramycin, atropine and prednisolone were administered. The clinical signs resolved completely, and to the best of our knowledge, primary pyomyositis with uveitis has not been previously reported in cats.

1. INTRODUCTION

Pyomyositis is a bacterial infection of skeletal muscle, often associated with abscessation (Patel et al., 1997). It can occur following direct muscle trauma (secondary pyomyositis) or as a result of haematogeous bacterial spread (primary pyomyositis). In humans, it is predominantly caused by Staphylococcus aureus and most commonly affects the quadriceps, gluteal, and iliopsoas muscles (Cherry et al., 2001). It generally responds well to antibiotic therapy but can prove fatal if treatment is delayed (Bickels et al., 2002). Parasitic infection (e.g. neosporosis, toxoplasmosis and hepatozoonosis) is the most common cause of infectious myositis in animals, but bacterial infection (e.g. leptospirosis, clostridial and rickettsial infections) is also commonly reported in dogs and cats (Podell, 2002). Additionally, feline immunodeficiency virus‐associated inflammatory myopathy has been described in the adult cat (Podell et al., 1998).

Pyomyositis is more common in tropical than in temperate climates, and in humans, characteristically occurs in adults with predisposing medical conditions, such as HIV infection, diabetes mellitus or alcoholic liver disease, and a history of recent trauma to the affected muscle group (Cherry et al., 2001). Primary pyomyositis is extremely rare in both human and veterinary patients.

Here we describe a cat with primary pyomyositis in which no underlying disease was found.

2. CASE PRESENTATION

A 6‐year‐old neutered male Siamese cat was referred to Jeju National University Veterinary Medical Teaching Hospital for investigation of hindlimb ataxia and blindness of 2 weeks’ duration. A change in iris colour from blue to yellow (Figure 1b) was also reported. On presentation, the cat was depressed but alert and responsive with normal body condition score. Physical examination revealed mild hyperthermia (39.5°C), mild tachycardia (heart rate 180 beats per minute), mild tachypnoea (respiratory rate 30 breaths per minute) and diffuse swelling of the right hind limb with no evidence of trauma (Figure 1a). Ophthalmic examination revealed change of iris colour, dyscoria, corneal opacity, chorioretinitis and an absence of menace responses bilaterally. Intraocular pressure (IOP) was 2 mmHg in the right eye (OD) and 3 mmHg in the left eye (OS) (reference interval 15–25 mmHg). A complete blood count (CBC) identified nonregenerative anaemia and neutropenia (haematocrit, 27.6%, reference interval, 30.3−52.3%; neutrophil 440/μL, reference interval, 1480−10,290/μL). Blood smear evaluation revealed severe toxic neutrophil changes (cytoplasmic vacuolation, cytoplasmic basophilic and Döhle bodies) and a left shift (Figure 2a). Serum biochemistry analysis identified elevated serum amyloid A ([SAA] 89.6 μg/mL; reference interval, 0−5 μg/mL), creatine kinase ([CK] 1099 U/L; reference interval, 0–314 U/L) and aspartate aminotransferase ([AST] 178 U/L; reference interval, 0–48 U/L). Routine coagulation tests were performed because the cat was critically ill; and activated partial thromboplastin time was prolonged ([aPTT] > 2000 s; reference interval, 86−137 s) and prothrombin time was within the reference range. Point‐of‐care serology tests and external polymerase chain reaction (PCR) testing for feline immunodeficiency virus, feline leukaemia, and toxoplasma were negative. Thoracic radiography and abdominal ultrasonography were unremarkable. Cytology of fine needle aspiration samples taken from the right hindlimb swelling revealed degenerate neutrophils and bacterial cocci (Figure 2b). Furthermore, Streptococcus canis was identified by bacterial identification test (Supporting information 1). Based on the results of the clinical examination and laboratory tests, the patient was diagnosed with primary pyomyositis and uveitis.

FIGURE 1.

Photographs showing swollen right hind limb without signs of trauma (a) and changed iris colour (b; blue to yellow).

FIGURE 2.

Cytology of peripheral blood smear, showing band cells (yellow arrow), and neutrophils with basophilic cytoplasm, cytoplasmic vacuolation and Dohle bodies (red arrow) consistent with left shift and toxic change (a). Fine needle aspirate sample taken from the swollen right hind limb showing degenerate neutrophils (yellow arrow) and bacterial cocci (red circle) (b). × 400.

During hospitalisation, the cat received intravenous fluid therapy with buffered crystalloid (2.5–5 mL/kg/h), analgesia (remifentanil; 6 μg/kg/h) and a combination of broad‐spectrum antibiotics (amoxicillin‐clavulanic acid, 20 mg/kg, intravenous, q12 h; marbofloxacin, 2 mg/kg, per oral, q24 h; metronidazole, 7.5 mg/kg, intravenous, q 12 h) for 3 days. Additionally, the cat received topical prednisolone acetate 1% eye drops (q 8 h), atropine 1% eye drops (q 12 h) and tobramycin‐containing ophthalmic solution (q 8 h). Since SAA levels had not improved after 3 days of broad‐spectrum antibacterial therapy, a Penrose drain tube was placed to facilitate drainage of the purulent discharge (Figure 3), and the previous antibacterial drugs were replaced with clindamycin (12.5 mg/kg, per oral, q12h) on receipt of the bacterial susceptibility test results (Supporting information 1). Subsequently, SAA, CK, AST and citrate aPTT values improved markedly over the next few days. The Penrose drain was removed on day 9, and the cat was discharged from the hospital on day 12. Treatment with oral clindamycin for primary pyomyositis, and topical prednisolone acetate 1% (q8 h), atropine 1% (q 12 h) and tobramycin‐containing ophthalmic solution (q 8 h) for uveitis were continued. On reassessment, 4 weeks later, SAA (Figure 4a), AST (Figure 4b), CK (Figure 4c) and citrate aPTT (Figure 4d) were within the reference interval, and the neutropenia had resolved. In addition, the ataxia was much improved, and with the exception of persistent fibrin strands, the ocular abnormalities had resolved (Figure 5). All medications were discontinued and no recurrence was reported at the 6‐month follow‐up.

FIGURE 3.

Penrose drain tube placement to facilitate purulent fluid drainage from the right hind limb swelling.

FIGURE 4.

Serial changes in serum amyloid A (SAA; reference interval, 0−5 μg/mL) (a), creatine kinase (CK; reference interval, 0–314 U/L) (b), aspartate aminotransferase (AST; reference interval, 0–48 U/L) (c) and activated partial thromboplastin time (aPTT; reference interval, 86−137 s) (d) during treatment.

FIGURE 5.

Patient appearance following treatment showing normal demeanour, resolution of hindlimb swelling, and marked improvement of ocular changes including return of normal iris colour.

3. DISCUSSION

To the best of our knowledge, primary pyomyositis has not been previously reported in cats. In addition, the lack of underlying disease and presence of concurrent uveitis are of specific interest.

Although well described in patients with preexisting medical conditions, primary pyomyositis has rarely been reported in immunocompetent humans (Bickels et al., 2002). Cherry et al. (2001) reported an unusual case of thoracoabdominal pyomyositis caused by group A beta‐haemolytic Streptococcus infection in a previously healthy young woman who had no history of local trauma. Minami et al. (2017) reported thigh pyomyositis caused by group A Streptococcus in an immunocompetent adult without any underlying cause, and Knees et al. (2018) reported Gram‐negative pyomyositis in an immunocompetent patient. Elzohairy (2018) reported primary pyomyositis in 15 children and concluded that primary pyomyositis can occur in individuals of all ages. To our best knowledge, primary pyomyositis has not been reported in the veterinary literature. It is notable that the location (thigh) and bacterial species (Streptococcus) in the cat described here show similarities with the previously reported human literature.

It is widely acknowledged that uveitis can be associated with systemic inflammation in humans (Jammal et al., 2021). Kulpati et al. (1990) have previously reported anterior uveitis as a complication of tropical pyomyositis in humans. Massa et al. (2002) have retrospectively reported that 42% of dogs with uveitis had concurrent systemic disease such as inflammation and neoplasia; therefore, they recommended extensive diagnostic tests in addition to anti‐inflammatory therapy. Another retrospective study revealed that 6 of 356 dogs with surgically treated pyometra were diagnosed with concurrent uveitis (Jitpean et al., 2014). Furthermore, uveitis has been reported in a cat with septic peritonitis (Pumphrey et al., 2011). Postulated mechanisms for uveitis as a complication of systemic inflammation/infection include the effects of cytokines, bacterial toxins and other inflammatory mediators on the blood–ocular barriers (Pumphrey et al., 2011). In this case, uveitis is thought to have been triggered by systemic inflammation resulting from primary pyomyositis, and to our knowledge, this has not been previously described in the veterinary literature.

In humans, it is well described that critically ill patients have increased contact activation with concomitant factor XII consumption, leading to aPTT prolongation (Bachler et al., 2019). Moreover, recent work has also proven that factor XII‐deficiency is a common finding among critically ill people, particularly those with sepsis and septic shock (Bachler et al., 2019). In dogs, Cheng et al. (2009) have reported that inflammation delays thrombin generation, as reflected by prolonged activated clotting time and aPTT. Therefore, the prolonged aPTT observed in this cat is assumed to have been related to severe inflammation. The possibility of a spurious result at the point of initial testing cannot be excluded.

In humans, early initiation of empirical intravenous antibiotics may suffice in the initial stage of pyomyositis (Fernández et al., 2021). However, if an abscess is detected, most recent studies recommend drainage or surgery prior to initiation of antibiotic therapy (Elzohairy, 2018; Fernández et al., 2021). In this patient, there was no improvement with initial broad‐spectrum antibacterial drugs alone; however, it is unclear whether the subsequent resolution was due to the drainage, or to the change in antibiotic therapy.

4. CONCLUSION

Pyomyositis and concurrent uveitis is reported in a cat with no apparent underlying disease. Resolution was achieved following antibacterial therapy and placement of a Penrose drain.

AUTHOR CONTRIBUTIONS

Jongjin Park: writing original draft, formal analysis. Saeyoung Lee: investigation, formal analysis. Minkun Kim: investigation, formal analysis. Hyohoon Jeong: investigation, formal analysis. Youngmin Yun: investigation, formal analysis. Woo‐Jin Song: conceptualisation, supervision, writing – review & editing.

CONFLICT OF INTEREST STATEMENT

The authors declared no potential conflicts of interest.

ETHICS STATEMENT

The cat described in this report was a client‐owned patient presented for care at the Veterinary Medical Teaching Hospital of Jeju National University. Informed owner consent was received for any possible research use of all diagnostic samples acquired from the patient.

PEER REVIEW

The peer review history for this article is available at https://publons.com/publon/10.1002/vms3.1224.

Supporting information

Supporting Information

Park, J. , Lee, S. , Kim, M. , Jeong, H. , Yun, Y. , & Song, W.‐J. (2023). Primary pyomyositis and uveitis in a cat. Veterinary Medicine and Science, 9, 1959–1964. 10.1002/vms3.1224

DATA AVAILABILITY STATEMENT

Data available on request due to privacy/ethical restrictions.