Paramedullary plasma cell myeloma originating from the first cervical vertebra ( <scp>C1</scp> ) in an 8‐month‐old Warmblood with tetraparesis: Clinical and pathological findings

Summary To the authors' knowledge there is only one report in the literature describing plasma cell paramedullary myeloma in horses as so‐called ‘break out lesions’, originating from vertebral bone marrow and invading the epidural space. This report describes clinical and pathomorphological findings of such. An 8‐month‐old Warmblood colt exhibited acute tetraparesis and a cervical column spinal cord lesion was suspected. Computed tomography revealed C1 osteolytic lesions by a heterogeneous mass. By pathomorphological examination including transmission electron microscopy, a plasma cell myeloma was identified, locally compressing the spinal cord. In tetraparetic young horses traumatic spinal cord injuries, cervical vertebral malformations, and central nervous system infectious diseases represent common differentials. However, osteolytic tumours such as paramedullary (plasma cell) myelomas, as space occupying lesion due to vertebral canal intrusion, should be considered as a cause for severe neurological deficits.