Nemaline Rods in Canine Myopathies: 4 Case Reports and Literature Review

Abstract

The diagnosis of nemaline rod myopathy (NM) is based on the presence of numerous pathognomonic rods within a fresh frozen muscle biopsy specimen. Three forms of congenital NM have been described in humans, and rods have been found to occur in various other conditions. A similar myopathy was described in 1986 in a family of cats. In this report. we describe a case of congenital NM in a 10-month-old Border Collie, an adult-onset NM in an 1 I-year-old Schipperke, and 2 acquired myopathies with nemaline rods in adult dogs associated with hypothyroidism and Cushing's syndrome. Common clinical features included exercise intolerance, abnormal electromyography, and the presence of nemaline rods in fresh, frozen, and glutaraldehyde-fixed biopsies from proximal appendicular limb muscles. Staining of cryostat sections of muscle biopsy specimens by the modified Gomori trichrome technique disclosed numerous rod bodies that were localized to type 1 fibers by the histochemical adenosine triphosphatase reaction. Accumulation of rods also was demonstrated by electron microscopy in 2 of the cases with localized enlargement and streaming of Z lines. Documentation of NM in a young Border Collie and the adult-onset form in the Schipperke alerts clinicians to the existence of this disorder in these breeds.

Hypothyroidism

“…A subclinical myopathy has been well-documented in hypothyroid dogs and also occurs in experimental models of canine hypothyroidism (Delauche, 1998;Rossmeisl et al, 2009). Hypothyroid myopathy is accompanied by increased plasma creatine kinase, aspartate aminotransferase, and lactate dehydrogenase activities.…”

Tetraparesis, Hemiparesis, and Ataxia

“…893 Signs develop between 6 weeks and 7 months of age and are generally much less severe than those in the X-linked dystrophy. 606,902 Distal Myopathy of Rottweilers. These dog often show adduction of the hock and carpal joints.…”

“…953 Pelvic limb stiffness may be unilateral or bilateral and eventually may involve the thoracic limbs (Figure 7-26). 824,902 The muscle weakness will improve in some dogs upon withdrawal of exogenous corticosteroids or suppression of endogenous corticosteroids. Severe pelvic limb rigidity develops in some dogs.…”

Adult‐onset nemaline myopathy in a dog presenting with persistent atrial standstill and primary hypothyroidism

“…As small numbers of rod bodies can be found in muscle fibres in other disorders including human immunodeficiency virus (Simpson and Bender 1988), polymyositis (Cape and others 1970) or hypothyroidism (Reyes and others 1986), a diagnosis of NM can only be made when rod bodies are present in more than 40% of muscle fibres (Reyes and others 1986). In the veterinary literature, rod bodies have been reported in rare cases of congenital and adult‐onset canine NM (Delauche and others 1998), and associated with hypothyroidism (Delauche and others 1998, Rossemeisl and others 2009). However, none had evidence of cardiac abnormalities nor was long‐term follow‐up available to evaluate the progression of the disease.…”