Perosomus elumbis, cerebral aplasia, and spina bifida in an aborted Thoroughbred foal

Perosomus elumbis represents a rare congenital anomaly characterized by aplasia of the lumbosacral spinal cord and vertebrae. This anomaly is often associated with arthrogryposis and malformations of the urogenital and intestinal tract. This report describes the first case of perosomus elumbis in an aborted Thoroughbred foal associated with cerebral aplasia with meningocele, cranioschisis, spina bifida, a fused urogenital and intestinal tracts lined by a cutaneous mucosa without uterine glands, atresia ani, and arthrogryposis of the hind legs. Immunohistochemistry detected no abnormalities in the GFAP, S-100, vimentin, NeuN, doublecortin, and neurofilament expression pattern in the remnants of the brainstem. Pathogenic bacteria or equine herpesviruses one and four were not found using a microbiological investigation or polymerase chain reaction, respectively. The observed malformations may be induced by a severe developmental disturbance during the formation of the neural tube with secondary distortion of the surrounding mesoderm. Although the aetiology of this dysorganogenesis remains undetermined, inherited chromosomal mutations, an intake of different xenobiotics, and/or a disturbed metabolism of the mare may have caused the defect.