Chronic eosinophilic granulomatous tenosynovitis in a Quarter Horse mare

Abstract

A 5-year-old Quarter Horse mare was presented to the Michigan State University Equine Surgery Service for evaluation of a right hind metatarsophalangeal joint injury. On presentation, the horse was a grade 4/5 lame. Radiographs and ultrasonography showed peritendinous ossification/mineralisation of soft tissue structures and digital flexor tenosynovitis with profound intracapsular mineralisation. A digital flexor tendon sheath tenoscopy was performed with a plantar annular ligament desmotomy and a manica flexoria ligament tenotomy. During surgery, a significant amount of tan granular material was found within the digital tendon sheath. Approximately 80% of this material was removed, and a sample was sent for histopathology. The horse was diagnosed with eosinophilic granulomatous tenosynovitis. Long-term follow-up revealed improvement with four treatments of intralesional triamcinolone given 2-4 weeks apart. The horse became serviceably sound (grade 1/5) and was beginning light work under the saddle approximately 5 months post-tenoscopy.

Tendon sheath masses – What are the differential diagnoses and what diagnostics are needed?

“…Ultimately, more diagnosed cases will be needed to answer all of these questions and will be dependent on thorough clinical examination, imaging examination, synovial fluid analysis prior to surgical intervention or joint lavage, and diligent follow‐up. The current case report by Williams et al (2022) highlights the necessity of such information and adds a new clinical differential diagnosis to our list for masses within a tendon sheath.…”

“…These horses were seen within 1–2 weeks post‐injection. In the current case report by Williams et al (2023), the digital flexor tendon sheath had also been injected but was not presented for referral evaluation until approximately 3 months after the start of lameness and approximately 2 months after injection at which time severe lameness was observed as well as profound mineralisation on radiographic and ultrasonographic examination. Is this difference in presentation simply due to time and progression of the disease or does eosinophilic synovitis within the deep digital flexor tendon sheath truly present with a granulomatous appearance?…”

“…An important point in this current case report by Williams et al (2023) is the potentially critical information that could be obtained from analysis of the digital flexor tendon sheath fluid. Whilst sampling is easy to perform in effusive digital flexor tendon sheaths (Horne et al, 2019; Jordana et al, 2012; Rocconi & Sampson, 2013), and fluid is often drained prior to injection of the sheath for treatment, rarely is this fluid submitted for analysis.…”

“…Williams et al (2023) describe the first reported case of eosinophilic granulomatous deep digital flexor tenosynovitis in a horse. The presence of eosinophils in the tendon sheaths and joints of horses affected with mastocytosis has been previously reported (Leadbeater et al, 2010; Uehlinger et al, 2010; Williams & van den Boom, 2020), but these mastocytosis cases appear to be a separate entity from both the current case and other reported cases of intra‐articular eosinophilic synovitis (Climent et al, 2007; DiDomenico et al, 2021; Madison & Zimmer, 1993; Turner et al, 1990).…”