Extending the length of the diaphyseal and proximal metaphyseal regions of the third metatarsal bone, a large amount of smoothly marginated osseous proliferation is identified. This osseous proliferation is most distinct at the distal one-third of the dorsal aspect of the cortex of the third metatarsal bone.
Within the metatarsal region, the soft tissue are mildly to moderately thickened.
Thoracic radiographs:
Throughout the pulmonary parenchyma, primarily ventrally distributed, a moderate to severe unstructured interstitial pulmonary pattern is identified. Within the ventral thoracic region, this pattern coalesces into an alveolar pattern and silhouettes with the heart margins and ventral margin of the diaphragm. Poorly defined nodular soft tissue opacities are seen superimposed on the caudal vena cava and cranial one-third of the intrathoracic trachea.
Conclusions:
Moderate to severe bilateral metatarsal III periosteal proliferation with soft tissue swelling, predominantly attributed to hypertrophic osteopathy. Changes secondary to periostitis are considered less likely.
Mixed alveolar and interstitial pulmonary pattern, with suspected pulmonary nodules. Differentials should include fungal pneumonia such as with aspergillosis, bacterial pneumonia (r/o Rhodococcus equi), or infiltrative neoplasia.
Follow-up:
Medical record is incomplete. Infectious diseases testing was performed.
A little bit more…
Hypertrophic osteopathy is rare. Many theories as to how hypertrophic osteopathy develops have been suggested; however, the underlying pathogenesis remains unclear (Enright et al., Bayless et al.).
Associated primarily with intrathoracic disease, such as neoplasia, pneumonia, rib fractures and pulmonary thromboembolization (Enright et al., Lavoie et al., Mair et al.).
Tuberculosis has previously been reported as the most common cause of hypertrophic osteopathy in horses, and fewer cases has been reported since its decline (Enright et al., Lavoie et al.).
A higher prevalence in thoroughbred is possible; however, too few cases are reported to validate (Enright et al.).
Clinical signs are often nonspecific and may include chronic weight loss. Musculoskeletal changes may be noted before clinical manifestation of the underlying cause (Lavoie et al.).
Radiographs are valuable to support a diagnosis (Enright et al.).
Radiographic features (Enright et al., Lavoie et al.):
Periosteal proliferation involving the diaphyses and/or metaphyses of the affected bones (most commonly the third metacarpal/metatarsal bones and/or mandible).
The noted osseous proliferation is most often smooth, spiculated or has a palisade-like appearance perpendicular to the cortex, with the more chronic cases having a smoother contour.
The articular surfaces were not affected in all reported cases.
The osseous changes are most commonly symmetrical.
Regional soft tissue swelling is common.
Image Gallery
Mandibular involvement could be an indicator of disease progression and severity (Enright et al.).
Successful treatment of the primary underlying disease condition often results in cessation of hypertrophic osteopathy with improvement and occasionally resolution of the associated osseous changes (Enright et al., Lavoie et al.).
References:
Enright K, Tobin E, Katz LM. A review of 14 cases of hypertrophic osteopathy (Marie’s disease) in horses in the Republic of Ireland. Equine Veterinary Education. 2011 May;23(5):224-30.
Mair TS, Dyson SJ, Fraser JA, Edwards GB, Hillyer MH, Love S. Hypertrophic osteopathy (Marie’s disease) in Equidae: a review of twenty‐four cases. Equine veterinary journal. 1996 Jul;28(4):256-62.
Lavoie JP, Carlson GP, George L. Hypertrophic osteopathy in three horses and a pony. Journal of the American Veterinary Medical Association. 1992 Dec 15;201(12):1900-4.
Bayless R, Almes K, Choudhary S, Beard W, Garcia E, Biller D. Hypertrophic osteopathy in a three-year-old quarter horse mare. Israel Journal of Veterinary Medicine. 2014 Sep 1;69(3).
