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| | ***Grossly: | | ***Grossly: |
| | ****Thickened and edematous periskeletal soft tissue and periosteum of the lower legs | | ****Thickened and edematous periskeletal soft tissue and periosteum of the lower legs |
| − | ****Multifocal [[Parasitic Myositis|parasitic myositis]] | + | ****Multifocal [[Muscles Inflammatory - Pathology#Parasitic myositis|parasitic myositis]] |
| | ***Histologically: | | ***Histologically: |
| | ****Swelling and hypertrophy of osteoprogenitor cells | | ****Swelling and hypertrophy of osteoprogenitor cells |
| | ****Hyperplasia of spindle cells | | ****Hyperplasia of spindle cells |
| | ****Osteoid is produced | | ****Osteoid is produced |
| − | | + | *[[More Hepatozoon|More detail on ''Hepatozoon americanum'']] |
| − | *Myositis | |
| − | **Develop cysts in skeletal muscle of dogs and cats
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| − | **May be accompanied by pyogranulomatous myositis - macrophages and [[Neutrophils|neutrophils]] mainly with occasional other cells
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| − | '''[Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum. Panciera Rj et al. Vet Path (2000) 37 225-230]'''
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| − | *[[Coccidia|'''''Hepatozoon americanum''''']]
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| − | **SE USA
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| − | **Clinical signs:
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| − | ***Fever
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| − | ***Weakness
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| − | ***Myalgia
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| − | ***Bone pain
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| − | ***Mature neutrophilic leukocytosis
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| − | ***Wasting
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| − | ***Poor response to treatment
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| − | ***Periosteal new bone formation
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| − | **Much more aggressive and higher mortality rate than the disease in the Old World
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| − | **Gross skeletal lesions:
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| − | ***Markedly thickened and edematous periskeletal soft tissue and periosteum of the lower legs ***+/- petechiation
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| − | ***Eccentrically or circumferentially arranged plaques of new bone formation deposited on the original cortex
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| − | ***Boney plaques look ‘porous’ to compact, often in layers with the spongey areas covered by more compact bone
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| − | ***No evidence of endosteal bone formation
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| − | ***Periosteoproliferative lesions most prominent in proximal long bones of the limbs (esp. femur and humerus)
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| − | ***Metaphyses usually spared
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| − | ***Caudal and lateral surfaces of the proximal tibia and fibular and radius and ulnar diaphyses affected
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| − | ***Distal diaphyses and metaphyses less severely affected/free from lesions
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| − | ***Metacarpals/tarsals mildly affected
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| − | ***Lateral surface of scapula affected
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| − | ***Axial skeleton less severely affected
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| − | ***Often bones of the skull prominently affected – orbits, rostrolateral maxilla and mandible, lateral aspect of zygomatic arch
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| − | ***Lateral aspects of vertebral arches and spinous processes sometimes affected
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| − | ***Ribs normal
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| − | ***Multifocal [[Parasitic Myositis|parasitic myositis]]
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| − | **Histologically:
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| − | ***Earliest change in periosteum -> swelling and hypertrophy of osteoprogenitor cells in the deeper layers of the periosteum
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| − | ***Spindle cells become stellate and plumper
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| − | ****Become aligned in single or multiple layers
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| − | ****Undergo hyperplasia creating a thick and densely cellular zone on the cortical surface
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| − | ***Osteoid is produced and osteoblasts become entrapped forming spiccules of trabecular new bone
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| − | ***New spicules arranged perpendicular to the cortical surface
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| − | ***With time, considerable osteoclastic activity, remodeling occurs firstly adjacent to the older cortex and then extends outwards
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| − | ***As the remodeling continues, the spicules become longitudinally arranged
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| − | ***Pseudocortices form that can contain bone marrow parenchyma
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| − | ***Endothelial hypertrophy prominent in vessels adjacent and within the periosteum
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| − | ***Severe edema present in adjacent soft tissue
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| − | ***Muscle atrophy and fibrosis often accompanied the edema
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| − | ***No evidence of inflammation
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| − | ***No parasites in adjacent muscle/soft tissue
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| − | **Lesions develop in young dogs, within 5wks of experimental infection and progress rapidly, looking just like hypertrophic osteopathy
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| − | **No obvious link between site of infection and generalized boney lesions
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| − | *Differentials for periosteal new bone formation:
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| − | **[[Hypertrophic Osteopathy|Hypertrophic osteopathy]]
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| − | **[[Craniomandibular Osteopathy|Craniomandibular osteopathy]]
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| − | **[[Panosteitis|Canine panosteitis]]
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| − | **[[Hypertrophic Osteodystrophy|Hypertrophic osteodystrophy]]
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| − | *Hypertrophic osteoarthropathy
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| − | **V difficult to distinguish from this syndrome
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| − | **Again no inflammation, histologically look identical, but these cases don’t have an abdominal/thoracic mass, and HO usually starts on the metacarpals/tarsals
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| − | *?Pathogenesis
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| − | **Thought to occur secondary to increased blood flow and fluid retention within the limbs, leading to vascular and then periosteal proliferation
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| − | [[Category:Miscellaneous Protozoa]][[Category:To_Do_-_Parasites]]
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| − | [[Category:Bones - Pathology]]
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