JPC SYSTEMIC PATHOLOGY
Musculoskeletal System
March 2019
M-M04

Signalment (JPC #2333663):  Newborn, male Romney lamb

HISTORY:  This lamb was one of approximately 50 lambs stillborn from a flock of 450 ewes.  Six other lambs had similar connective tissue abnormalities including skin fragility, joint laxity, blue sclera, soft bones, brittle teeth, multiple bone fractures and long bones with thickened diaphyses without distinct medullary cavities. 

HISTOPATHOLOGIC DESCRIPTION:  Slide B (H&E):  Alveolar bone, tooth and mucosal surface:  Diffusely there is marked osteopenia characterized by a lack of cortical bone and markedly thin trabeculae of woven bone that are irregular, basophilic and multifocally lined by variably thick layers of flattened osteoblasts with decreased osteoid production and rare osteoclasts.  Trabecular (woven) bone is often hypercellular with increased numbers of haphazardly arranged osteocytes within enlarged and multifocally coalescing lacunae.  Trabeculae are widely separated by abundant, loosely arranged mesenchymal tissue admixed with multifocal variably dense areas of fibrous connective tissue.   Multifocally there are trabecular microfractures and areas of hemorrhage, fibrin, and edema.  The tooth has a disorderly arrangement of odontoblasts with piling up and loss of polarity and diffuse irregularity in the thickness of predentin.  The dentin is thin, irregular, and scalloped with many parallel wavy basophilic lines (mineralization fronts) and marked reduction and loss of dentin tubules (dysplasia).  Enamel is multifocally absent (lost during processing).

Slide A (van Gieson):  Alveolar bone, tooth and mucosal surface:  There is a diffuse decrease in collagen (red staining) content, characterized by osteopenia with thin trabeculae and lack of cortical bone and irregularity of dentin.

MORPHOLOGIC DIAGNOSIS

  1. Alveolar bone:  Osteopenia, diffuse, moderate, with trabecular dysplasia, Romney, ovine.
  2. Tooth: Dentin dysplasia, diffuse, marked. 

CONDITION:  Osteogenesis and dentinogenesis imperfecta

SYNONYM:  Brittle bone disease

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURE

DIFFERENTIAL DIAGNOSIS:

Gross:

Conditions with abnormal metaphyseal bone (abnormal, thin spongiosa):

Causes of osteoporosis (reduced bone density/mass):

Causes of tooth lesions:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barnes A, Carter E. Lack of cyclophilin B in osteogenesis imperfect with normal collagen folding. N Engl J Med. 2010; 362: 1940-1941.
  2. Craig LE, Dittmer KE, Thompson KG. Bones and joints. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 7th ed. St. Louis, MO: Elsevier; 2016:46-50.
  3. Eckardt J, Kluth S. Population screening for the mutation associated with osteogenesis imperfect in dachshunds. Vet Rec. 2013; 172: 364-366.
  4. Kamoun-Goldrat AS, Le Merrer MF. Animal models of osteogenesis imperfecta and related syndromes. J Bone Miner Metab. 2007; 25(4):211-218.
  5. Laine CM, Joeng KS, Campeau PM, Kiviranta R, et al. WNT1 mutations in early-onset osteoporosis and osteogenesis imperfecta. N Engl J Med. 2013; 368(19):1809-1816.
  6. Olson EJ, Carlson CS. Bones, joints, tendons and ligaments. In:  McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017: 973-974.
  7. Seeliger F, Leeb T, Peters M, Brugmann M, Fehr M, Hewicker-Trautwein M. Osteogenesis imperfecta in two litters of Dachshunds. Vet Pathol. 2003; 40:530-539.
  8. Van Dijk FS, Zllikens MC, Micha D, Riessland M, et al. PLS3 mutations in X-linked osteoporosis with fractures. N Engl J Med. 2013; 369(16):1529-1536.


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