CASE DESCRIPTION: A 4-MONTH-OLD MALE, ROTTWEILER DOG REFERRED TO OUR HOSPITAL WITH HISTORY OF LETHARGY, DEHYDRATION, VOMITING, POLYURIA AND POLYDIPSIA FOR A FEW DAYS.CLINICAL FINDINGS: THE PHYSICAL EXAMINATION REVEALED PALE MUCOUS MEMBRANES, FLEXIBLE JAWS ON FIRM PALPATION (RUBBER JAW SYNDROME) AND LOOSENS MOST OF THE TEETH RESULTING FROM RESORPTION OF ALVEOLAR BONE. PATIENT SHOWED IN LAST DAYS SHIFTING LAMENESS AS WELL. RADIOGRAPHIC EXAMINATION OF THE SKULL REVEALED GENERAL REDUCED BONE DENSITY. THE DOG COULD EAT ONLY SOFT FOOD AND WAS UNDERWEIGHT. LABORATORY EVALUATION REVEALED NON-REGENERATIVE (HYPOPLASTIC) ANAEMIA IN RESULT OF SYNTHETIZE AND SECRETE ERYTHROPOIETIN IN THE KIDNEYS, AZOTAEMIA AND HYPERCHOLESTEROLEMIA, HYPERPHOSPHATEMIA. PROTEINURIA AND ISOSTHENURIA WERE FOUND ON THE URINALYSIS.TREATMENT AND OUTCOME: RENAL DYSPLASIA WITH SECONDARY HYPERPARATHYROIDISM WAS DIAGNOSED BASED ON HAEMATOLOGY AND SERUM CHEMISTRY SCREEN, RADIOLOGICAL FINDINGS AND HISTOPATHOLOGY. THE DOG WAS EUTHANATIZED WITH REQUEST OF THE OWNER AND EXTREMELY POOR PROGNOSIS.CLINICAL RELEVANCE: HYPERPARATHYROIDISM HAS BEEN RECOGNISED FOR MANY YEARS AS A POTENTIALLY SERIOUS COMPLICATION OF CHRONIC RENAL FAILURE.CHRONIC RENAL FAILURE OCCURS MOST FREQUENTLY IN ADULT AND AGING DOGS BUT IS UNCOMMON IN JUVENILE OR YOUNG DOGS, IN WHICH IT IS OFTEN THE CONSEQUENCE OF A HEREDITARY NEPHROPATHY. THE MAIN CATEGORIES OF FAMILIAL NEPHROPATHIES ARE RENAL DYSPLASIA, PRIMARY GLOMERULOPATHIESPOLYCYSTIC KIDNEY DISEASE, AMYLOIDOSIS, AND GLOMERULONEPHRITIS. RENAL DYSPLASIA IS DEFINED AS A DISORGANIZED RENAL DEVELOPMENT DUE TO AN ABNORMAL DIFFERENTIATION OF THE PARENCHYMA. THE DISEASE IS CHARACTERISED BY THE PRESENCE OF STRUCTURES THAT ARE INAPPROPRIATE FOR THE STAGE OF DEVELOPMENT OF THE ANIMAL. BESIDE, RENAL OSTEODYSTROPHY IS A COMMON LONG-TERM COMPLICATION OF END-STAGE RENAL DISEASE THAT FREQUENTLY DESCRIBED IN DOGS. INVOLVEMENT OF THE JAWS IS COMMON AND RADIOGRAPHIC ALTERATIONS ARE OFTEN ONE OF THE EARLIEST SIGNS OF CHRONIC RENAL DISEASE. HOWEVER, IN MOST CASES, LESIONS ARE CHARACTERIZED BY FIBROUS OSTEODYSTROPHY OF FACIAL BONES, AFFECTING PRINCIPALLY THE MANDIBLE AND THE MAXILLA.