Hereditary myotonia in cats associated with a new homozygous missense variant p.Ala331Pro in the muscle chloride channel ClC-1

Three-related cats were evaluated for a history of short-strided gait and temporary recumbency after startle. Neurological examination, electromyography (EMG), muscle biopsies, and a chloride voltage-gated channel 1 (CLCN1) molecular study were performed. Clinically, all 3 cats presented myotonia with warm-up phenomenon and myotonic discharges during EMG examination. Muscle biopsies showed normal muscle architecture and variation in the diameter of myofiber size with the presence of numerous hypertrophic fibers. The molecular study revealed a missense variant (c.991G>C, p.Ala331Pro) in exon 9 of the CLCN1 gene, responsible for the first chloride channel extracellular loop. This mutation was screened in 104 control phenotypically normal unrelated cats, and all were wildtype. The alanine at this position is conserved in ClC-1 (chloride channel protein 1) in different species, and 2 mutations at this amino acid position are associated with human myotonia. This is the third CLCN1 mutation described in the literature associated with hereditary myotonia in cats and the first in domestic animals located in an extracellular muscle ClC-1 loop.

Hereditary myotonia in American Bulldog associated with a novel frameshift mutation in the CLCN1 gene

Hereditary myotonia (HM) is a genetic disorder that occurs due to mutations in the chloride channel and results in delayed relaxation of the skeletal muscles. HM has been described in 12 dog breeds, and in five of them, molecular studies of this disorder were performed and mutations in the CLCN1 gene were described. In this study, an affected American Bulldog with HM clinically characterized by muscle hypertrophy, myotonic discharges, and nondystrophic myotonia with a "warm-up" phenomenon was evaluated, and the candidate canine CLCN1 gene was sequenced. The molecular analysis revealed a frameshift mutation NM_001003124.2:c.436_437insCTCT that resulted in a frameshift and a premature stop codon NP_001003124.1:pTyr146SerfsTer49 . Two aberrant alternative CLCN1 transcripts were observed in an affected dog, the expected transcript with the 4 bp insertion, NM_001003124.2:r.436_437insctct, and an unexpected transcript containing parts of intron 6 in addition to the insertion in exon 4, NM_001003124.2:[r.436_437insctct;r.774_775ins79]. In conclusion, the frameshift mutation in the CLCN1 gene is associated with autosomal recessive HM in American Bulldog and this study constitutes the first description of the disease in this breed.

Infiltrative Lipoma Causing Lumbar Nerve Root Compression in a Dog

Background: Lipomas are benign soft tissue mesenchymal neoplasms composed of adipose cells and are usually found in the subcutaneous tissue. Occasionally, lipomas may invade muscles or grow between them, in which case they are characterized as infiltrative lipomas. Clinical signs resulting from an intermuscular lipoma compressing peripheral nerves are rarely encountered in dogs. This case report aims to describe the neurological signs, diagnosis, and clinical evaluation of a dog diagnosed with infiltrative lipoma compressing a lumbar spinal nerve root.Case: A 12-year-old neutered male Fox Paulistinha, weighing 10.5 kg, was presented with difficulties in walking for the past 15 days with no previous history of trauma. On physical examination, the presence of three cutaneous nodules was noted in the ventral thoracic region, with onset of one year and slow and progressive growth. A cytological evaluation of the nodules was performed, and lipoma was diagnosed. At the neurological examination, the patient presented ambulatory paraparesis with marked motor deficit and atrophy of the quadriceps muscles of the left pelvic limb. Conscious proprioceptive deficit, the absence of patellar reflex, and diminished withdrawal reflex were observed in the left hind limb, in addition to diffuse pain on epaxial palpation of the lumbar region. Electroneuromyography showed increased insertion activity in the left gastrocnemius muscle and moderate spontaneous activity (fibrillation). Persistence of 10% was observed in the F-wave study of the left tibial nerve. These findings indicate partial involvement of the roots of the left sciatic-tibial nerve. Magnetic resonance imaging (MRI) showed the presence of a mass measuring 3.18 × 1.04 × 1.4 cm, interspersed with the paravertebral muscles, and located adjacent to the L2 and L3 spinous processes. An ultrasound-guided fine needle aspiration biopsy of the mass was performed and the findings of the cytopathological analysis of the collected material were considered consistent with lipoma. In view of these findings, surgical removal was recommended. However, the owner chose to attempt conservative treatment to control pain. Thus, the patient was treated with gabapentin, tramadol hydrochloride, carprofen, dipyrone, omeprazole, and physiotherapy. The animal exhibited a good response to conservative treatment, regaining its hind limb mobility in approximately 30 days.Discussion: Infiltrative lipomas compressing nerve roots are rarely described, with only one report of infiltrative lipoma in the lumbar region causing nerve root compression in dogs found in the literature. MRI was beneficial in this case, since it helped in determine the shape, location, and extent of the mass causing compression of the left L2 nerve root. The history and neurological examination findings in the patient described in this report were accounted for by the presence of an infiltrative lipoma compressing the left nerve root of L2. Surgical excision is the treatment of choice for intramuscular lipomas in most cases since conservative treatment elicits only a limited response. In contradiction to the literature, the dog in this report experienced a good response to conservative treatment, returning to normal mobility approximately 30 days after starting treatment. After six months of follow-up, the dog had not experienced a recurrence of the clinical signs. However, since the tumor has not been removed, clinical relapse is expected to occur in the future. Thus, despite the good response to conservative treatment in this case, we recommend the surgical excision of the tumor in order to decompress the affected nerve root. Although infiltrative lipomas compressing nerve roots are rare, clinicians should consider them as differential diagnosis when there is a presence of subcutaneous lipomas and neurologic signs of radiculopathy.

PROLAPSO DE GLÂNDULA DE TERCEIRA PÁLPEBRA EM CÃES: AVALIAÇÃO CITO E HISTOPATOLÓGICA

No presente trabalho dez cães apresentandoglândulas da terceira pálpebra prolapsadasforam submetidos à excisão cirúrgica e avaliaçãocito e histopatológica. A idade dos cães varioude dois meses a dez anos, sendo das raças Beagle(20%), Teckel (10%), Pinscher (10%), Poodle (10%)e SRD. As glândulas removidas foram aspiradaspor agulha fina para o exame de citologia aspirativae a seguir, fixadas em formalina a 10% e coradaspor HE. Aos cortes histológicos foi possívelobservar infiltrado inflamatório predominantementemononuclear focal na conjuntiva e região periacinar.Observou-se dilatação no lúmen dos ductos emetaplasia. No exame citológico, notou-se infiltradoinflamatório semelhante ao histopatológico. Asglândulas apresentaram uma adenite crônica. Aausência de mudanças cito e histopatológicas notáveisdemonstrou um tecido glandular funcional nomomento da excisão cirúrgica.

Histopathological evaluation of treatment with chondroitin sulphate for osteoarthritis induced by continuous immobilization in rabbits

The aim of this study was to evaluate histologically the action of chondroitin sulphate in osteoarthritis experimentally induced by continuous immobilization. Fourteen young female Norfolk rabbits aged 2.5-3 months at the beginning of the experiment were divided into two equitable groups submitted to immobilization of the right knee for a period of 12 weeks. The treated group received 1.0 ml/animal/s.c. of 12% chondroitin sulphate, once a week for 12 weeks, and the untreated group did not receive any treatment. Two additional animals were not submitted to knee immobilization (sham group). Microscopical examination of knee preparations stained with haematoxylin-eosin and Masson trichrome showed lesions of both joints in treated and untreated groups, with no significant difference between the scores obtained for the right and left knees. Examination of preparations stained with picrosirius red showed collagen fibre alignment and misalignment in the right and left knees of the animals of all groups, but statistic analysis could not be performed. It was not possible to differentiate the proteoglycan concentration between limbs or groups (treated and untreated) by safranin O or toluidine blue staining. It was possible to conclude that the chondroitin sulphate was not able to reduce the histological changes induced by this osteoarthritis experimental model.

Radiography, computed tomography and magnetic resonance imaging at 0.5 Tesla of mechanically inducedosteoarthritis in rabbit knees

In the present experimental study we assessed induced osteoarthritis data in rabbits, compared three diagnostic methods, i.e., radiography (XR), computed tomography (CT) and magnetic resonance imaging (MRI), and correlated the imaging findings with those obtained by macroscopic evaluation. Ten young female rabbits of the Norfolk breed were used. Seven rabbits had the right knee immobilized in extension for a period of 12 weeks (immobilized group), and three others did not have a limb immobilized and were maintained under the same conditions (control group). Alterations observed by XR, CT and MRI after the period of immobilization were osteophytes, osteochondral lesions, increase and decrease of joint space, all of them present both in the immobilized and non-immobilized contralateral limbs. However, a significantly higher score was obtained for the immobilized limbs (XT: P = 0.016, CT: P = 0.031, MRI: P = 0.0156). All imaging methods were able to detect osteoarthritis changes after the 12 weeks of immobilization. Macroscopic evaluation identified increased thickening of joint capsule, proliferative and connective tissue in the femoropatellar joint, and irregularities of articular cartilage, especially in immobilized knees. The differences among XR, CT and MRI were not statistically significant for the immobilized knees. However, MRI using a 0.5 Tesla scanner was statistically different from CT and XR for the non-immobilized contralateral knees. We conclude that the three methods detected osteoarthritis lesions in rabbit knees, but MRI was less sensitive than XR and CT in detecting lesions compatible with initial osteoarthritis. Since none of the techniques revealed all the lesions, it is important to use all methods to establish an accurate diagnosis.