Limbal squamous cell carcinoma in Haflinger horses.

OBJECTIVE: To describe the prevalence of LSCC in Haflinger horses and to analyze affected horses' pedigrees investigating the genetic mode of inheritance. ANIMALS: Fifteen horses met inclusion criterion of (i) being of the Haflinger breed, as confirmed by North American Haflinger Registry pedigree and (ii) being diagnosed with LSCC, as confirmed by clinical examination by a veterinary ophthalmologist or by histopathology. Pedigrees could not be obtained for four additional horses diagnosed with LSCC that had been identified as Haflingers. PROCEDURE: Retrospective medical record review of all 19 horses was used to determine patient sex and age at diagnosis. The four-generation pedigrees available for 15 of the horses were used to perform pedigree analysis. RESULTS: Average age of 19 Haflingers at diagnosis with LSCC was 8.7 years. Eleven were males and eight were females. Thirteen of 15 affected horses for whom pedigrees were available shared a common ancestor within five generations, and all 15 shared a common ancestor from the A stallion line in the breed pedigree. Pedigree analysis identified a common sire of two of the affected male horses. Clinical examination of this sire that had no history of LSCC showed no current clinical signs of LSCC, suggesting an autosomal recessive mode of inheritance. CONCLUSIONS: Haflingers may be over-represented amongst horses with LSCC and may be diagnosed at a younger age than other breeds. Affected Haflingers appear closely related, suggesting a possible heritable basis for LSCC. The genetic basis for LSCC will be investigated further by a GWAS approach.

Corneal dystrophy in Friesian horses may represent a variant of pellucid marginal degeneration.

OBJECTIVE: To describe the clinical presentation, treatment, and outcome of a corneal dystrophy in Friesian horses and to analyze affected horses' pedigrees to investigate its heritability. ANIMALS: Nine Friesians with bilateral disease were identified. PROCEDURE: Retrospective medical record review was used to identify Friesian horses exhibiting bilateral symmetric corneal lesions. Variables identified from medical records included patient sex and age at diagnosis; location, depth and size of corneal lesions; medical and surgical therapy instituted; and visual outcome. A four-generation pedigree for each included horse was used to construct a combined pedigree. RESULTS: The nine included horses had an average age at diagnosis of the first eye of 10.7 years, with males (8/9) significantly more frequently affected than females (1/9), P = 0.012. Lesions were inferior and averaged 5 mm in diameter. Depth ranged from superficial facets to perforations, which developed in nine of 18 eyes. Eight of nine perforations were surgically repaired, with seven of eight repaired eyes visual at last follow-up. All nine eyes that had not perforated remained visual. All affected horses shared a common ancestor within six generations. CONCLUSIONS: This form of corneal dystrophy in Friesian horses, characterized by bilateral symmetric stromal loss, appears to be progressive but responds well to surgical repair, occurs more frequently in males, may have a genetic component in Friesian horses, and may be a variant of pellucid marginal degeneration.