Surgical management of osteochondromatosis affecting the vertebrae and trachea in an Alaskan Malamute

Multiple cartilaginous exostoses in a Swiss Mountain dog causing thoracolumbar compressive myelopathy

BACKGROUND

Multiple cartilaginous exostoses are a rare, benign, proliferative condition of cartilage and bone. They can be asymptomatic, or they may cause pain, lameness, paresis and even paralysis, depending on their location and size. In cases of spinal cord or nerve root compression, surgery is the treatment of choice. Therefore, an advanced imaging diagnostic work-up is indicated. Due to the unclear pathophysiology and progression of this condition, it is difficult to predict its prognosis.

CASE PRESENTATION

A 9-month-old female Swiss Mountain dog was presented with a history of gait abnormalities, kyphosis and hypersensitivity consistent with a thoracolumbar myelopathy. Multiple calcified masses, most prominent at the Th7-Th9 level and the L2-L3 level, were observed. Magnetic resonance imaging of the thoracolumbar vertebral column revealed severe dorsal spinal cord compressions near the dorsal arch of the Th7-Th9 and L2-L3 vertebrae. Two of these masses were removed surgically. The successful removal of both masses was confirmed by postoperative computed tomography. The histopathological examination of the resected tissue revealed multiple cartilaginous exostoses. The first neurological and magnetic resonance follow up examination carried out 6 months postoperatively showed improvement of the clinical status. At that time, no mass regrowth was observed. The last follow up neurological examination carried out 15 months postoperatively showed gait improvement and resolution of pain.

CONCLUSION

This is the first case report of multiple cartilaginous exostoses with a complete pre- and postoperative evaluation and a 15 month follow-up.

Surgical management of myelopathy caused by a solitary spinal osteochondroma in a young cat

Case summary

A 10-month-old, male castrated, domestic shorthair cat was presented with fast-progressing ataxia of the pelvic limbs. MRI and CT were performed, revealing a bony proliferation at T11, with mass effect and laterodorsal compression of the spinal cord. After hemilaminectomy and the removal of the bony mass, the cat recovered uneventfully. At the 1 year follow-up, the cat did not show any neurological deficits or signs of recurrence.

Relevance and novel information

Solitary osteochondroma as a cause of neurological deficits in the pelvic limb has been described in dogs and humans, but, to the best of our knowledge, there are no reported feline cases described in the literature, in which CT and MRI were performed in combination with the successful removal of the lesion and an excellent outcome for the patient.

Cartilaginous Tumors of the Larynx and Trachea in the Dog

Cartilaginous tumors of the larynx and trachea are uncommon in the dog. The authors describe 10 cases diagnosed between 1995 and 2014 and review 16 cases in the literature. Seven of our cases were tracheal and 3 were laryngeal. Two of the laryngeal tumors were chondromas, which have not been previously reported in this site. The third laryngeal tumor was a myxochondroma. Of the 7 tracheal tumors, 6 arose from the ventral tracheal wall, including 2 that were extraluminal. Tracheal tumor types included chondrosarcoma ( n = 3), chondroma ( n = 2), and osteochondroma ( n = 2). All of the laryngeal tumors and 5 of 7 of the tracheal tumors occurred in adult dogs (aged 5–11 years). The 2 tracheal osteochondromas were in young dogs (3–4 months) and were intrathoracic, while the remaining tracheal tumors were cervical. Surgical excision had a good outcome in most cases. Combining our 10 cases with the 16 previously reported cases showed that 6 (27%) of the affected dogs were Arctic breeds (Alaskan Malamute or Siberian Husky) suggesting a predisposition in this type of dog.

Identification and functional characterization of the human EXT1 promoter region

BACKGROUND

Mutations in Exostosin-1 (EXT1) or Exostosin-2 (EXT2) cause the autosomal dominant disorder multiple osteochondromas (MO). This disease is mainly characterized by the appearance of multiple cartilage-capped protuberances arising from children's metaphyses and is known to display clinical inter- and intrafamilial variations. EXT1 and EXT2 are both tumor suppressor genes encoding proteins that function as glycosyltransferases, catalyzing the biosynthesis of heparan sulfate. At present, however, very little is known about the regulation of these genes. Two of the most intriguing questions concerning the pathogenesis of MO are how disruption of a ubiquitously expressed gene causes this cartilage-specific disease and how the clinical intrafamilial variation can be explained. Since mutations in the EXT1 gene are responsible for ~65% of the MO families with known causal mutation, our aim was to isolate and characterize the EXT1 promoter region to elucidate the transcriptional regulation of this tumor suppressor gene.

METHODS

In the present study, luciferase reporter gene assays were used to experimentally confirm the in silico predicted EXT1 core promoter region. Subsequently, we evaluated the effect of single nucleotide polymorphisms (SNP's) on EXT1 promoter activity and transcription factor binding using luciferase assays, electrophoretic mobility shift assays (EMSA), and enzyme-linked immunosorbent assays (ELISA). Finally, a genotype-phenotype study was performed with the aim to identify one or more genetic modifiers influencing the clinical expression of MO.

RESULTS

Transient transfection of HEK293 cells with a series of luciferase reporter constructs mapped the EXT1 core promoter at approximately -917 bp upstream of the EXT1 start codon, within a 123 bp region. This region is conserved in mammals and located within a CpG-island containing a CAAT- and a GT-box. A polymorphic G/C-SNP at -1158 bp (rs34016643) was demonstrated to be located in a USF1 transcription factor binding site, which is lost with the presence of the C-allele resulting in a ~56% increase in EXT1 promoter activity. A genotype-phenotype study was suggestive for association of the C-allele with shorter stature, but also with a smaller number of osteochondromas.

CONCLUSIONS

We provide for the first time insight into the molecular regulation of EXT1. Although a larger patient population will be necessary for statistical significance, our data suggest the polymorphism rs34016643, in close proximity of the EXT1 promoter, to be a potential regulatory SNP, which could be a primary modifier that might explain part of the clinical variation observed in MO patients.

Analysis of tidal breathing flow volume loop in dogs with tracheal masses

OBJECTIVES

To investigate whether there are any changes in the tidal breathing flow volume loop (TBFVL) in calm, non-dyspnoeic dogs with intratracheal masses.

METHODS

We compared 4 dogs with intratracheal masses (group 1) with 10 healthy dogs (group 2). Routine clinical and laboratory examinations of the dogs were unremarkable, except for episodic upper respiratory obstructive signs in the dogs in group 1. Lateral radiography of the neck and thorax showed that group 1 dogs had masses that appeared to protrude into the tracheal lumen. Tracheoscopy and surgery or necropsy was performed to confirm the presence of the mass. Arterial blood gas and TBFVL analysis was carried out in all dogs to assess respiratory status.

RESULTS

The shape of the TBFVL for dogs in group 1 was narrower and ovoid compared with that for the group 2 dogs. Tidal volume and expiratory and inspiratory times were significantly reduced, whereas the respiratory rate was increased for dogs in group 1 compared with dogs in group 2. Arterial blood gas analysis was unremarkable for all dogs.

CONCLUSIONS

TBFVL is a non-invasive technique that is easy to perform and well tolerated by dogs. In the absence of abnormalities detected by routine diagnostic evaluations and arterial blood gas analysis in dogs with intratracheal masses, the TBFVL contributes to the definition of the physiologic status of the airways at the time of testing, and results suggests that these dogs breathe quite normally when they are calm and non-dyspnoeic.