Immune-Mediated Polyarthritis
November 17, 2025 · Case Study
IMPA Case Summary – Finley Recknor
Patient: Finley, 4-year-old neutered male German Shepherd mix
Date of Initial Presentation to AVES: May 27, 2025
Presenting Concern: Lethargy, progressive facial/ocular swelling, and hindlimb swelling
History and Presentation:
Finley was initially noted by the family on May 22, 2025, to be lethargic with bilateral periorbital swelling that progressed toward the muzzle. Evaluation by the primary care veterinarian revealed hindlimb joint effusion. Cytopoint and prednisone 10 mg once daily therapy were initiated. Over the subsequent days, his condition worsened, with decreased appetite and progressive ocular swelling. On May 27, Finley was presented to AVES.
Physical Examination at AVES:
Mentation: Quiet, alert, responsive
Marked bilateral chemosis (conjunctival swelling)
Joint effusion in both carpi, tarsi, and stifles
Ambulatory x4 with no ataxia, full neurologic exam not performed
Diagnostics:
C-reactive protein: Markedly elevated at 33.2
CBC/Chem (5/23): Hct 60.8, Plt 156, ALT 125
Ophthalmic tests: STT OS 18 mm/min, OD 6 mm/min
In-house joint cytology (left carpus): Neutrophilic inflammation
Tick-borne disease panel: Bartonella titer 1:64 (seropositive), PCR negative
Submitted joint cytology (4 joints):
60–82% non-degenerate neutrophils
Ample mucin and proteinaceous fluid
No organisms or malignant cells
These findings support a diagnosis of immune-mediated polyarthritis (IMPA).
Diagnosis Overview: Immune-Mediated Polyarthritis (IMPA)
IMPA is an inflammatory joint disorder in which the immune system mistakenly attacks the synovial lining of multiple joints, resulting in pain, swelling, and systemic signs such as fever or lethargy. It can be:
Primary (idiopathic): No clear underlying cause is identified
Secondary: Triggered by infections (e.g., tick-borne diseases), medications, neoplasia, or other immune-related conditions
Diagnosis is based on clinical signs, joint cytology, and exclusion of infectious causes. Treatment typically includes immunosuppressive therapy, most commonly prednisone, and pain management. Prognosis is generally good, especially for dogs that respond promptly to initial treatment.
Treatment goals include:
Reducing joint inflammation and pain
Preventing relapses
Identifying and managing any underlying triggers (e.g., tick-borne illness)
Tapering immunosuppressive medications over time to the lowest effective dose.
In some cases, this allows for complete discontinuation of medication.
In other cases, it involves transitioning to lower doses of steroids or switching to a different immunosuppressive agent for long-term control.
Assessment:
Immune-Mediated Polyarthritis (IMPA)
Markedly elevated CRP consistent with systemic inflammation
Joint cytology negative for infectious organisms or neoplasia
Bartonella seropositive at 1:64 (low titer), but PCR negative
In uncomplicated, steroid-responsive IMPA, and especially with only low-titer seropositivity and negative PCR, doxycycline is not required. At this time, Bartonella is interpreted as an incidental finding or past exposure.
Treatment Initiated (5/27/25):
Prednisone 40 mg/m² by mouth every 24 hours (~40 mg daily)
Large breed dogs metabolize drugs slower per kilogram than small dogs. If we dose them using mg/kg, they can get too much medication, leading to more side effects.
Using mg/m² (based on body surface area) adjusts for metabolic differences.
Gabapentin 10 mg/kg by mouth every 8-12 hours for pain control
NeoPolyDex ophthalmic ointment ¼ inch strip in each eye every 12 hours for chemosis
Follow-Up (1 Week Later):
Finley is doing extremely well following initiation of immunosuppressive therapy. The family reports:
Full return to normal activity and energy level including running and jumping
Complete resolution of chemosis
No residual joint swelling noted at home
Plan:
Consider long-term management plan with Internal Medicine to taper steroids to the lowest effective dose.
Monitor CRP to determine treatment efficacy and guide tapering decisions.
