Nemaline rods in canine myopathies: 4 case reports and literature review

The diagnosis of nemaline rod myopathy (NM) is based on the presence of num erous pathognomonic rods within a fresh frozen muscle biopsy specimen. Thre e forms of congenital NM have been described in humans, and rods have been found to occur in various other conditions. A similar myopathy was describe d in 1986 in a family of cats. In this report, we describe a case of congen ital NM in a 10-month-old Border Collie, an adult-onset NM in an 11-year-ol d Schipperke, and 2 acquired myopathies with nemaline rods in adult dogs as sociated with hypothyroidism and Gushing's syndrome. Common clinical featur es included exercise intolerance, abnormal electromyography, and the presen ce of nemaline rods in fresh, frozen, and glutaraldehyde-fixed biopsies fro m proximal appendicular limb muscles. Staining of cryostat sections of musc le biopsy specimens by the modified Gomori trichrome technique disclosed nu merous rod bodies that were localized to type 1 fibers by the histochemical adenosine triphosphatase reaction. Accumulation of rods also was demonstra ted 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 t his disorder in these breeds.