Musculoskeletal System
March 2019
M-M09 (NP)

Signalment (JPC #1171672):  11-month-old female black spider monkey (Ateles fusciceps robustus)

HISTORY:  This monkey had a misshapen skull and long bones.

HISTOPATHOLOGIC DESCRIPTION: Slide A:  Tooth with alveolar bone, mandible (per contributor):  Cortical (compact) bone is thinned or absent and there is diffuse loss of alveolar and mandibular bony trabeculae (osteopenia).  Remaining thin, irregular trabeculae of woven bone are lined by rare osteoblasts and increased numbers of osteoclasts within Howship’s lacunae (active resorption) with distinct resting and reversal lines. Osteoclasts are also free within the fibrous stroma.  Trabeculae are surrounded and widely separated by haphazardly arranged spindle cells (fibroblasts) admixed with dense, well-vascularized fibrous connective tissue that replaces normal hematopoietic elements and adipose tissue and extends to the adjacent periosteal surface. 

MORPHOLOGIC DIAGNOSIS:  Alveolar and mandibular bone (per contributor):  Fibrous osteodystrophy, diffuse, severe, black spider monkey (Ateles fusciceps robustus), nonhuman primate.

HISTOPATHOLOGIC DESCRIPTION:  Slide B:  Long bone:  Diffusely, cortical compact bone, and metaphyseal and diaphyseal cancellous bone is thin to absent and widely separated by increased amounts of loose fibrous connective tissue and fibroblasts that multifocally replace myeloid adipocytes and hematopoietic cells.  Multifocally, there are variably sized clusters of osteoclasts within Howship's lacunae (bone resorption).  Focally, the physis is expanded up to twice normal by a thickened zone of hypertrophy.  Small blood vessels in this area form irregular channels into the cartilaginous matrix.  There are retained fragmented cores of cartilage in the primary spongiosa, which are often surrounded by variable amounts of homogeneous eosinophilic matrix (osteoid).  There is an overall decrease in the number of osteoblasts.  Within the epiphyseal growth plate, there are additional areas of retained unmineralized cartilage.  There is a focal 1 x 1.5 mm diameter subchondral cyst in the epiphysis. 

MORPHOLOGIC DIAGNOSIS:  Long bone:  Fibrous osteodystrophy, diffuse, marked with focal physeal osteochondrodysplasia (rachitic).

ETIOLOGIC DIAGNOSIS:  Nutritional secondary hyperparathyroidism

CAUSE:  Dietary vitamin D3 deficiency and/or dietary calcium/phosphorus imbalance

SYNONYMS:  Simian bone disease; cage paralysis







Microscopically (fibrous osteodystrophy):



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Click on image for diagnostic series.

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