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Calvarial Hyperostosis Syndrome in an American Pit Bull/Terrier/Amerikan Pit Bull Terrier bir Kopekte Calvarial Hiperosteozis Sendromu.


Calvarial Hyperostosis Syndrome (CHS) is a recently defined rare osteopathy characterized by non-neoplastic proliferation of the fat bones of the skull (Pastor et al., 2000; McConnell et al., 2006; Mathes et al., 2012). Clinically and histologically, it resembles craniomandibular osteopathy and infantile cortical hyperostosis in humans (Pastor et al., 2000; Huchkowsky, 2002; Kamoun-Goldrat and Le Merrer, 2008; Varollo et al., 2012). Calvarial hyperostosis syndrome has been reported mostly in Bullmastiffs and case reports are available with respect to the presence of the disease in a Pit Bull Terrier and an English Springer Spaniel dog (Pastor et al., 2000; McConnell et al., 2006; Thompson et al., 2011; Mathes et al., 2012). The most prominent clinical manifestations are painful swelling of the skull bones, lymphadenopathy, eosinophilia and fever (Muir et al., 1996; Pastor et al., 2000; Thompson et al., 2011). Seizures, hydrocephalus, lameness and osteomyelitis are additional symptoms (Pastor et al., 2000; Thompson et al., 2011; Mathes et al., 2012).

To our knowledge, this is the first reported case of a dog with Calvarial Hyperostosis Syndrome in Turkey and we aimed to describe this case with its clinical and pathological aspects as a contribution to literature due to its rarity in dogs (Pastor et al., 2000; McConnell et al., 2006; Mathes et al., 2012) and to inform veterinary practitioners regarding the disease.


A four-month-old female American Pit bull terrier was referred to the clinic of the Faculty of Veterinary Medicine, Department of Surgery with complaints of painful swelling to the head, loss of appetite, lethargy and fever. Clinical inspection revealed firm bilateral swelling of the parietal and frontal bones of the skull and difuse edema extending to the right upper eyelid. (Figure 1a). Radiography of the skull revealed difuse thickening of the frontal and parietal bones and markedly increased bone opacity (Figure 1b). Magnetic resonance imaging scans revealed increased diploe thickness in all sequences. No pressure related distortions were observed on the brain parenchyma (Figure 1c).

No abnormalities were observed on routine biochemical screening tests or in the hemogram and the dog tested negative for canine distemper virus, parvovirus and coronavirus using immunochromatographic assay. In addition, a biopsy sample was taken from the bone tissue for histopathological evaluation.

The patient was monitored until one year of age and the swelling in the lesioned area was observed to have enlarged and expanded. Symptomatic treatment was prescribed including steroids and nonsteroidal anti-infammatory drugs to relieve pain. She was reported to have died at the age of 14 months due to poor care.

Bone biopsy samples harvested from the lesioned area were initially fixed in 10% formalin solution for 36 hours and then kept in a 5% nitric acid solution for 48 hours for decalcification. After routine tissue processing protocols, the specimens were embedded in paraffin, cut to a thickness of 4-5 [micro]m and stained with Hematoxylin and Eosin. Histopathologically, compact bone tissue composed of thickened trabeculae was observed in the sections. The bone trabeculae consisted of two structures: immature woven bone and mature trabeculae (Figure 2a). The trabeculae appeared thickened with narrowed medullary spaces which were replaced by highly vascular intermediate fbrosis and a few osteoblastic and osteoclastic cells were also seen (Figure 2b). Prominent basophilic cement lines were noted between these two structures (Figure 3a, b).


Calvarial Hyperostosis Syndrome, which has recently been defined in juvenile dogs, is a non-neoplastic bone disease characterized by the swelling of the skull (Pastor et al., 2000; McConnell et al., 2006; Mathes et al., 2012). This syndrome has been most commonly reported in Bullmastiffs (Pastor et al., 2000; McConnell et al., 2006), and occasionally, in other breeds (Thompson et al., 2011; Mathes et al., 2012). This is the first reported case of canine CHS in a Pit Bull Terrier with its clinical, radiological and histopathological aspects in Turkey.

This condition was reported only in juvenile dogs and whether or not gender affects susceptibility to the disease is still a matter of debate (Pastor et al., 2000; McConnell et al., 2006; Mathes et al., 2012). In the presented case, the disease was encountered in a 4-month-old female Pit Bull. Clinical signs of the disease included painful swelling of the skull bones, lymphadenopathy, eosinophilia and fever (Muir et al., 1996; Pastor et al., 2000; Thompson et al., 2011). Hydrocephalus, lameness and purulent osteomyelitis were also reported (Pastor et al., 2000; Thompson et al., 2011; Mathes et al., 2012). No other symptoms except for bilateral swelling of the parietal and frontal bones of the skull and fever were detected in the presented case.

Calvarial Hyperostosis Syndrome is a rare condition in dogs and it has been most commonly reported in young Bullmastif dogs (Pastor et al., 2000; McConnell et al., 2006). The clinical and histopathological traits of the syndrome resemble those of canine craniomandibular osteopathy (Alexander, 1983; Gulanber et al., 2001; Huchkowsky, 2002) and human infantile cortical hyperostosis (Kamoun-Goldrat and Le Merrer, 2008). The anatomic location of the lesion is of great importance in the differential diagnosis (McConnell et al., 2006; Mathes et al., 2012). In the presented case, the lesion was diagnosed as calvarial hyperostosis since the lesion developed bilaterally in the parietal and frontal regions of the skull and there was no evidence of mandibular involvement on the basis of clinical and radiographic findings.

It has been reported that there was prominent periosteal and subperiosteal infammation in the bone tissue in the cases of calvarial hyperostosis (Pastor et al., 2000; Thompson et al., 2011; Mathes et al., 2012). No signs of infammation were detected in the presented case. After the initial referral to the clinic, the patient was administered 2 mg/kg methylprednisolone sodium succinate (Prednol, Mustafa Nevzat Drug Industry, Turkey) and 2 mg/kg carprofen (Rimadyl, Zoetis) twice a day in view of the fact that the painful swelling on the head might have resulted from the infammatory response in the soft tissues and temporary pain relief was achieved with this treatment. However, radiography and a bone tissue biopsy confirmed that the condition was hyperostosis. The lack of infammatory reaction in the biopsy sample was associated with the long-term use of steroid and nonsteroidal anti-infammatory drugs. De Heer et al. (2015) reported that infammatory changes correlated with the phase of the disease at the time of the biopsy. Histopathologically, calvarial hyperostosis is characterized by periosteal proliferation of the parietal and frontal bones and correspondingly thickening of these bones. (Pastor et al., 2000; McConnell et al., 2006; Thompson et al., 2011; Mathes et al., 2012). In the presented case, radiography and magnetic resonance imaging revealed asymmetrical calvarial thickening. Characteristic microscopic findings in hyperostosis included the development of new bone tissue, which appeared as marked thickening of the trabecular structures in the zone, and correspondingly, the narrowing of centrally located bone marrow spaces replaced by a highly vascular fbrous tissue and the presence of prominent basophilic cement lines between these thick, newly formed trabeculae and the mature bone tissue (McConnell et al., 2006; Thompson et al., 2011). Our findings were compatible with those of the abovementioned reports. Clinically and histopathologically, calvarial hyperostosis may occasionally be confused with osteoma since it is a localized bone growth. It is usually easy to differentiate the entity by careful microscopic evaluation. In osteomas, the spaces between the trabeculae are larger with the occasional presence of bone marrow elements and there is very scanty fbrous tissue (Milli and Haziroglu, 1997). In contrast, in hyperostosis, these spaces are narrow and contain large amounts of highly vascular fbrous tissue. Newly formed trabeculae appear thickened and basophilic cement lines are prominent (McConnell et al., 2006; Thompson et al., 2011). However, in osteomas, newly formed bone trabeculae are thin and cementing lines are not visible.

The etiology of calvarial hyperostosis is still unknown. Possible roles of Prostoglandin E1 and E2 have been suggested in some studies, in which elevated levels of serum prostaglandin E was detected in some children with infantile cortical hyperostosis, which is a similar disease to that found in humans in terms of clinical and histopathological aspects. It was reported in the same studies that collagen disorders might also have played a role in the onset of the disease (Gensure et al., 2005; Glorieux, 2005). Therefore, we consider that further detailed studies should be carried out to elucidate the causes in the etiology of canine calvarial hyperostosis.

Most cases of calvarial hyperostosis appear to be of a self-limiting nature. Once the bone tissue reaches maturity, the lesions may regress. Therefore, no specific treatment has been indicated.

In some incidents, the lesions were grossly and histopathologically confused with osteomyelitis and, thus, antibiotics were prescribed (Thompson et al., 2011). Nonsteroidal anti-infammatory drugs were administered in some cases to inhibit infammation and to relieve pain (De Heer et al., 2015). In the presented case, pain relief and resolution of edema were achieved using steroids and nonsteroidal antiinfammatory drugs. However, no regression was observed and the lesion continued to grow.


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Damla HAKTANIR (1) [iD], Ebru ERAVCI YALIN (2) [iD], Yalcin DEVECIOGLU (2) [iD], Alper DEMIRUTKU (2) [iD], Aydin GUREL (1) [iD]

(1) Department of Pathology, Istanbul University Faculty of Veterinary Medicine, Istanbul, Turkey

(2) Department of Surgery, Istanbul University Faculty of Veterinary Medicine, Istanbul, Turkey

Cite this article as: Haktanir, D., Eravci Yalin, E., Devecioglu, Y., Demirutku, A., Gurel, A., 2008. Calvarial Hyperostosis Syndrome in an American Pit Bull Terrier. Acta Vet Eurasia 44: 49-52

ORCID IDs of the authors: D.H. 0000-0001-5171-1927; E.E.Y. 0000-0002-0941-6745; Y.D. 0000-0002-8175-2321; A.D. 0000-0001-5788-1660; A.G. 0000-0002- 0266- 8771.

Address for Correspondence: Aydin Gurel * E-mail:

Received Date: 13 June 2017 * Accepted Date: 23 October 2017 * DOI: 10.5152/actavet.2018.009
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Title Annotation:Case Report
Author:Haktanir, Damla; Yalin, Ebru Eravci; Devecioglu, Yalcin; Demirutku, Alper; Gurel, Aydin
Publication:Journal of the Faculty of Veterinary Medicine
Date:Jan 1, 2018
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