Case study: A puzzling limp

Mel, a 9-year-old neutered Catahoula mix, initially presented with limping in his front left leg. He stopped using the leg acutely when he woke up in the morning, but throughout the day, he would use the limb with a prominent limp. On physical examination, Mel was limping but not expressing pain. There was no swelling or crepitus, and he had a normal range of motion in all joints. At the time, the owner elected for conservative treatment with carprofen (Rimadyl).

Mel returned a month later for continued limping. He responded well and stopped limping while taking carprofen, but once the medication was finished, the limping returned. Radiographs were performed at this visit, and there was concern for a periosteal reaction on the humerus. The radiographs were sent to a radiologist for consultation, and the results included the following:

• There was evidence of a smooth periosteal reaction associated with the cranial and caudal cortex of the proximal humerus of the left thoracic limb. A heterogeneous and sclerotic opacity was seen on the caudal aspect of the humerus.
• The right shoulder joint was normal.
• The left and right elbow joints were normal.

• The right and left manus were normal.

The conclusion and recommendations based on the findings are that chronic periosteal reaction is associated with the proximal left humerus. differential diagnosis (DDX) coccidioidomycosis, hepatozoonosis​, and less likely neoplasia. The final diagnosis requires a bone biopsy, and a polymerase chain reaction for infectious diseases was mentioned.

I discussed the results and recommendations with the client, including a bone biopsy and fungal testing. While waiting for the owner to decide whether they wanted to proceed, Mel developed swelling over his skull, causing a droopy eye, and he had epistaxis. Radiographs of the skull were taken, and there was increased soft tissue opacity of the left nasal passage, increasing my suspicion of a potential fungal infection. Radiographs of his leg were also retaken, and the lesion worsened. The owners elected to pursue fungal testing at this time, which was negative. The owners then elected to pursue a bone biopsy of the worsening lesion on the humerus, as well as a biopsy of the nasal passages.

Unfortunately, the results of the biopsies were not very rewarding. The nasal biopsy was consistent with rhinitis, with no infectious agents noted. The bone biopsy showed reactive bone with no infectious or neoplastic cells. At this time, referral was recommended but declined by the client, and they elected for a trial of steroids. Mel responded well to the steroids; the skull swelling and nosebleeds resolved, and he was limping less. Unfortunately, when the owner started to taper the medication, all the symptoms returned.

About a month later, he returned for a recheck. His radiographs were taken again and showed progression of his lesion on his humerus. I had an honest conversation with the client, explaining that although his initial radiographs were more suspicious of a noncancerous lesion, the progression made me more concerned about cancer. Mel was also in pain from this lesion. Surgical amputation would provide not only a definitive answer to what the lesion is but also pain relief. The owners elected to move forward with surgical removal.

The results of the histopathology of the limb were unfortunately conclusive for osteosarcoma. The owners did not want to pursue referral for continued treatment options and elected palliative care.

Unfortunately, Mel returned about 4 months later with labored breathing. Radiographs were taken, and large masses were identified in the chest. The owners elected for humane euthanasia.

I selected this case for many reasons. It was my first leg amputation in a large dog, which was very memorable. This case was a challenging one that initially presented as a likely infectious cause, but was incidentally complicated by an unrelated disease affecting the nasal passage.

I think this case is important to remember because if a dog is not improving, keep repeating the tests! So many times, I feel it is difficult for us as veterinarians to keep recommending the same test over and over, especially when we are having to do more tests like the fungal testing, nasal biopsy, and bone biopsy—and all of these tests were unrewarding. But because I was persistent in ensuring the owner returned for rechecks and that we continued to repeat testing, we were able to find a cause for the owner, and more importantly, I was able to make the patient more comfortable for as long as possible.

Chelsey Lufkin, DVM, believes that through quality, preventive medicine, we can help our pets live longer, healthier lives. She enjoys making lasting relationships with her clients and patients.