Idiopathic Diffuse Lipomatosis in Dogs

Background: Idiopathic diffuse lipomatosis is a rare disease in veterinary medicine. It is characterized by excessive proliferation of adipocytes, which results in the formation of fatty tumours throughout the body. In humans, this disease is also known as Madelung’s disease or multiple symmetric lipomatosis and is classifed as type I and II. The aim of this study was to investigate two cases of dogs diagnosed with idiopathic diffuse lipomatosis and compare their characteristics with those found in humans.Cases: Case 1 - A 3-year-old standard poodle female was taken for veterinary evaluation for a slow-growing tumoural lesion over the neck and trunk. The tumours measured >30 cm in diameter that caused irregular and protruding folds resulting in a signifcant loss of body architecture. No clinical signs of adjacent systemic disease were observed. Elliptical excisions of the skin revealed diffuse mature adipocytes and hyperplastic and dysplastic lipoblast hypertrophy of the panniculus, which was associated with epidermodermal hypotrophy and skin appendages. The combination of these fndings supported a diagnosis of idiopathic diffuse lipomatosis. The animal underwent surgical therapy. However, the clinical symptoms recurred within two months. Owing to the continuous recurrence of tumours and history of three other surgeries, it was decided to euthanize the animal. Case 2 - An 11-year-old female cocker spaniel preenting tumoural lesions of insidious evolution and widespread distribution. Clinical examination revealed the presence of multiple subcutaneous tumours in the lateral, lumbosacral, and abdominal regions of the pelvic limb. No clinical signs of adjacent systemic disease were observed. Biopsies of tumoural lesions also supported the diagnosis of idiopathic diffuse lipomatosis. The animal was fed a low-calorie diet, after which its body weight decreased without inducing any changes in tumour size. In addition, the animal underwent surgical treatment for removal of the largest tumours. After surgery, the animal was monitored for 1year and showed no tumour recurrence.Discussion: In veterinary medicine, lipomatosis is an extremely rare disease. Therefore, before diagnosing a case, it is necessary to exclude other proliferative disorders of the adipose tissue, among which, the most common are lipomas and liposarcomas. There are no genetic studies related to lipolytic activity or adipocyte proliferation in animals. However, it is believed that the aetiology of idiopathic diffuse lipomatosis is similar to the pathophysiology of the human form of multiple symmetrical lipomatosis, and could be associated with a primary lipid metabolism disorder. In this study, the two cases described showed a distinct distribution in the type of tumours. In case 1, the tumours were well defned and focused in the cervical and thoracic region, a pattern similar to human type I lipomatosis. However, in case 2, the fat accumulationswere diffuse and mainly located in the posterior region of the animal’s body similar to type II lipomatosis. No animals presented intra-abdominal or intrathoracic fat infltration, diagnosed by ultrasound or radiography. There is no description of any treatment capable of being effective. However, surgical procedures are recommended to minimize the occurrence of tumours and improve the quality of life of the affected animals. In the two cases described in this study, it was diffcult to completely resect the tumours. In the frst case, the recurrence of fatty deposits and performance of multiple interventions resulted in a poor quality of life of the animal, which was fnally euthanized to avoid further suffering. Therefore, frequentrecurrences might correlate with a poor prognosis in dogs.Keywords: fat, subcutaneous, tumour, skin.