JPC SYSTEMIC PATHOLOGY
MUSCULOSKELETAL SYSTEM
April 2019
M-T04

SIGNALMENT (JPC 1947713):  A male Sprague-Dawley rat

HISTORY:  This rat was on a chronic 2-year oral toxicity study.  Malocclusion and dental fractures were common in treated animals.  The surfaces of the incisors were white, thickened or pitted.  Frequently, the nasal, maxillary, frontal and parietal bones of treated rats were white, thickened, and rough compared to those of control animals.  The changes were bilaterally symmetrical.

HISTOPATHOLOGIC DESCRIPTION:  Cranium, cross section through maxillary sinuses:  Bilaterally, teeth contain disorganized cuboidal to columnar ameloblasts that occasionally pile up 4-5 layers deep and line an enamel layer that has scalloped borders, increased clear space separating the enamel matrix, and numerous variably sized, up to 10um diameter basophilic globules.  There are multifocal areas with thinning of ameloblasts and subsequent thinning of enamel.  The predentin and dentin layers are irregular, thickened 2‑3 times normal, and contain numerous variably sized and coalescing, up to 20um diameter, basophilic globules.  The odontoblastic layer is thickened up to 2 times normal by increased numbers of vacuolated odontoblasts.  Ameloblasts and odontoblasts occasionally contain similar basophilic globules.  Diffusely, trabecular bone of the maxilla and cranium is mildly thickened (osteosclerosis) and the matrix is disorganized with numerous basophilic resting and reversal lines, reminiscent of woven bone, and the bone has scalloped borders lined by osteoblasts, , and there are numerous basophilic globules within the tooth matrix (similar to the tooth matrix).  The medullary spaces are small and contain increased fibrous connective tissue.  Multifocally, within the subepithelial connective tissue of the floor of the maxillary sinuses are small aggregates of lymphocytes and plasma cells that form follicles.

MORPHOLOGIC DIAGNOSIS: 

  1. Teeth, bilateral:  Dysplasia, ameloblastic and odontoblastic, diffuse, moderate, with enamel loss and malformation, dentin malformation, and basophilic globular material within ameloblasts, odontoblasts, dentin and enamel, Sprague-Dawley rat, rodent.
  2. Cranium: Osteosclerosis, diffuse, mild, with intratrabecular basophilic globular material. 

ETIOLOGIC DIAGNOSIS:  Dental fluorosis and osteofluorosis

CONDITION:  Fluoride toxicity (fluorosis)

GENERAL DISCUSSION: 

PATHOGENESIS: 

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

ADDITIONAL DIAGNOSTIC TESTS: 

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY: 

REFERENCES: 

  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016: 315.
  2. Bock P, Peters M, Bago Z, Wolf P, Thiele, Baumgartner W. Spontaneously occurring alimentary osteofluorosis associated with proliferative gastroduodenopathy in rabbits. Vet Pathol. 2007;44:703-706.
  3. Craig LE, Dittmer KE, Thompson KG: Bones and joints. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 1, 6th ed. St. Louis: Elsevier; 2016:84-86.
  4. DeBay B, Jacob B, Oehme FW, Imerman P. Sodium fluoride/copper naphthenate toxicosis in cattle. J Vet Diagn Invest. 2007:19:305-308.
  5. Flueck WT, Smith-Flueck JA. Severe dental fluorosis in juvenile deer linked to a recent volcanic eruption in Patagonia. J Wildl Dis. 2013 Apr;49(2):355-66.
  6. Gelberg HB. Alimentary system and the Peritoneum, Omentum, Mesentery, and Peritoneal Cavity. In: Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier Inc; 2017:351.
  7. Hufschmid J, Beveridge I, Coulson G, et al. Skeletal pathology of eastern grey kangaroos (Macropus giganteus) exposed to high environmental fluoride levels in South-Eastern Australia. J Comp Pathol. 2015;153(2-3):167-84.
  8. Maas J. Fluorosis. In: Smith BP, ed. Large Animal Internal Medicine. 5th ed. St Louis, MO: Mosby; 2015:1122-1123.


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