Clinical and Pathological Features of Flexural Deformities Associated with Myopathies in Foals

Flexural deformities (FDs) are a common condition in foals. Therapy is typically initiated without a precise diagnosis, and the etiopathogenesis often remains unknown. This study aimed (1) to investigate the clinical and pathological findings in congenital FD cases in foals and (2) to retrospectively describe the abnormalities detected in muscle biopsies of foals affected by CFDs. For these purposes, a retrospective study of the findings of muscle biopsies taken from foals with FDs referred to the Department of Veterinary Medicine and Animal Production at the University of Naples Federico II was performed from January 2005 to February 2024. Anamnesis, physical examination, hematological and biochemical data, along with the findings of histopathological muscle biopsy analysis and follow-up, were recorded. The clinical records of 15 cases of FDs were evaluated. The main clinical symptoms included flexural limb deformities associated with weakness, torticollis and scoliosis, mandibular prognathism, and inferior eyelid entropion. The evaluation of histopathological reports allowed us to observe the following muscle disorders: Core-like myopathy, mild nonspecific myopathy, mitochondrial myopathy, congenital fiber type disproportion, lipid storage myopathy, lipomatous dystrophy, myopathy with inclusion bodies, polysaccharide storage myopathy, and neurogenic myopathy. Even though many cases of FDs were diagnosed through clinical examination and successfully treated, we hypothesize that different underlying etiologies may present with similar flexural symptoms. A better understanding of these underlying causes is, therefore, desirable. These findings suggest that histopathological analysis may be a valuable tool for investigating FDs in foals, although further studies are needed to evaluate the significance of the observed alterations.