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Case Reports
. 2022 Apr 27:9:872778.
doi: 10.3389/fvets.2022.872778. eCollection 2022.

American Canine Hepatozoonosis Causes Multifocal Periosteal Proliferation on CT: A Case Report of 4 Dogs

Cambridge L Coy  1 , Jeremy B Evans  1 , Alison M Lee  2 , Danielle R Dugat  3 , Jonathan M Levine  1 , John F Griffin 4th  4
Affiliations
Case Reports

American Canine Hepatozoonosis Causes Multifocal Periosteal Proliferation on CT: A Case Report of 4 Dogs

Cambridge L Coy et al. Front Vet Sci. .

Abstract

American canine hepatozoonosis (ACH) represents an important but relatively uncommon differential diagnosis in a dog with fever, muscle wasting, profound leukocytosis, and/or musculoskeletal pain. Despite this, obtaining a definitive diagnosis can prove difficult. Peripheral blood smears and whole-blood polymerase chain reaction (PCR) rely on rare parasitemia, and the gold standard diagnostic test (skeletal muscle biopsy) is uncommonly pursued due to its invasive and costly nature. Demonstration of characteristic periosteal proliferative lesions aids diagnosis. The lesions typically involve the more proximal long bones of the appendicular skeleton. The periosteal proliferation is of currently unknown pathogenesis, but its distribution is characteristic of this disease with few differential diagnoses. This case series describes the findings on computed tomography (CT) in 4 dogs with PCR- or cytologically-confirmed Hepatozoon americanum. All dogs had multifocal, bilaterally asymmetric, irregularly marginated, non-destructive, non-articular, periosteal proliferative lesions. Recognition of this unusual CT finding and awareness of this disease could assist in the diagnosis and subsequent treatment of dogs with ACH and may offer an additional indication for CT in cases of fever, muscle wasting, and myalgia.

Keywords: canis; case report; gulf coast; neutrophilia; periosteum; pseudocortex; tick.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Example of suspected lesions of American canine hepatozoonosis. Post-contrast transverse images at the level of the sixth cervical (A), second thoracic (B), fifth thoracic (C), and tenth thoracic vertebrae (D) in a in a 2 year-old female spayed miniature Australian shepherd dog who tested positive for Hepatozoon americanum polymerase chain reaction. In all images, there is multifocal, irregularly marginated, periosteal proliferation on several non-articular surfaces of the axial skeleton (white arrowheads). There is no lysis of cortical bone in any image. In (A), the ventral vertebral body and transverse processes are asymmetrically affected. The medial aspect of both scapulae have smooth periosteal proliferation that has organized to form a pseudocortex. In (B), the periosteal proliferation of the spine of the right scapula appears similar to the lesions on the ribs and vertebrae. The second pair of ribs have mild lesions. In (C), the left fifth rib has multifocal regions of irregular periosteal proliferation on the medial surface, while in (D) there is periosteal proliferation of the dorsal surface of the tenth ribs. There is no contrast enhancement seen in the soft tissues surrounding the periosteal proliferations.
Figure 2
Figure 2
Example of suspected lesions of American canine hepatozoonosis. Non-contrast transverse images of the second (A), third (B), and fourth cervical vertebrae (C) and a dorsal image at the level of the scapulae (D) in a 2 year-old male castrated Rhodesian ridgeback dog that tested positive for Hepatozoon americanum polymerase chain reaction. In all images, there is multifocal, irregularly marginated, periosteal proliferation on several non-articular surfaces of the vertebrae (white arrowheads). In (A), the ventral vertebral body, transverse processes and dorsal arch are asymmetrically affected. In (B), the lamina and ventral vertebral body have similar lesions that vary in thickness depending of the location. In (C), the periosteal proliferation is restricted to the ventral surface of the vertebra. None of the lesions bridge the space between adjacent vertebrae. In (D), the scapulae have mild asymmetric lesions on the medial aspect. The left scapula also has periosteal proliferation of the infraspinous fossa.
Figure 3
Figure 3
Example of suspected lesions of American canine hepatozoonosis. Non-contrast transverse images of the second (A), third (B), and fourth cervical vertebrae (C), as well as the first thoracic vertebra and scapulae (D) of a 6 year-old intact female miniature schnauzer dog in which a Hepatozoon americanum gamont was identified on a peripheral blood smear. In all images, there is multifocal, irregularly marginated periosteal proliferation on several non-articular surfaces of the vertebrae (white arrowheads). The underlying cortical margins are smooth, intact, and of normal thickness. In (A), the ventral vertebral body and transverse processes bilaterally have similar lesions that do not connect. In (B), the periosteal proliferation is lateralized to the right ventral vertebral body and transverse process. In (C), similar lesions are also seen on the dorsal spinous process and lamina. In (D), both medial and lateral surfaces of both scapulae are affected. This is an example of the marked asymmetry and irregularity of the periosteal proliferation.
Figure 4
Figure 4
Example of suspected lesions of American canine hepatozoonosis. Non-contrast transverse images of the fifth (A), sixth (B), and seventh lumbar vertebrae (C) and a sagittal image of the caudal lumbar vertebrae (D) in a 7 year-old male neutered Yorkshire terrier dog that tested positive for Hepatozoon americanum polymerase chain reaction. In all images, there is multifocal, irregularly marginated, periosteal proliferation on several non-articular surfaces of the lumbar vertebrae (white arrowheads). There is no lysis of cortical bone in any image. In (A), the lesions are restricted to the ventral vertebral body and transverse process. The periosteal proliferation is thick and forms a nearly continuous pseudocortex. The lesions in (B) are similar to (A), but highlight the asymmetry of the lesions. In (C), the pseudocortex is undulant and disappears axially. The periosteal proliferation is lateralized and equally prominent on the left pedicle of the sixth lumbar vertebra. In (D), smooth periosteal proliferation is present at the midventral vertebral body of the fourth and fifth lumbar vertebrae. The periosteal proliferation is widest at the middle of the vertebral body and tapers toward the intervertebral disc space. There is no bridging periosteal proliferation.
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