Thyroid dysgenesis associated with dwarfism, osteoporosis and spontaneous fractures in a goat

An 11-month-old female Saanen goat, weighing 12.7 kg, was taken to the Veterinary Hospital of the Federal University of Minas Gerais because of sternal recumbency. On clinical examination, the animal was much smaller than expected and had hair similar to that of puppies and areas of hyperpigmentation on the head and dorsocervical and dorsothoracic cranial regions. Radiographic examination revealed fractures in both femurs and severe generalized osteoporosis. Given the unfavourable prognosis, the animal was euthanized. Necropsy revealed generalized pallor, muscular atrophy of the pelvic limbs and little reserve of subcutaneous adipose tissue. Both femurs had complete and closed diaphyseal fractures. The second lumbar vertebra was severely reduced in length as a result of a fracture, with dorsal displacement of the vertebral body towards the vertebral canal and compression of the spinal cord. Long bones and vertebrae had severe cortical thinning, enlargement of the medullary canal and reduced resistance. The thyroid gland was not in its normal anatomical location. A pale red nodule (1.0 × 0.4 cm) in the serosa of the middle third of the trachea, close to the thoracic entrance, was confirmed as ectopic thyroid tissue. Microscopically, the bones had evidence of growth arrest and severe osteoporosis. The ectopic thyroid nodule was hyperplastic with severe hypertrophy of follicular cells. The spinal cord was compressed by vertebral fractures and had focally extensive and severe myelomalacia. Based on the pathological features, the case was diagnosed as thyroid dysgenesis characterized by eutopic thyroid agenesis and ectopic thyroid tissue, associated with interruption of bone growth with dwarfism, osteoporosis and spontaneous secondary fractures with compression of the lumbar spinal cord.