Glycogen storage disease in Norwegian Forest cats

© August, JR (2006) Consultations in Feline Internal Medicine, Vol 5.  Elsevier Saunders

A deficiency in glycogen branching enzyme alpha-1,4-D-glucan:alpha-1,4-D-glucan 6-glucosyl transferase has been reported as an autosomal recessive condition in Norwegian Forest cats. Clinical signs begin around 5 months of age with hyperthermia, generalised muscle atrophy, movement-associated whole body tremors and ataxic gait. These progress rapidly to tetraparesis with diminished myotactic and flexor reflexes, multiple cranial nerve dysfunction, seizures and eventually death.

Serum biochemical abnormalities include transient elevations in alanine aminotransferase activity and creatine kinase activity reflective of hepatic dysfunction and muscle necrosis, respectively. Electrophysiological studies including electromyography, peripheral nerve conduction studies, electroencephalography and somatosensory evoked potentials reflect loss of both central and peripheral neurones. Histologically, accumulation of glycogen material detected by periodic acid Schiff-haematoxylin (PAS) stain occurs in multiple organs including lymph nodes, lungs, gastrointestinal tract, liver, thymus, cardiac and skeletal muscle, and central and peripheral nervous systems. Glycogen accumulations in neurons result in neuronal loss and axonal degeneration. Similar findings are observed in motor, sensory, and autonomic nerves. The genetic defect has been characterised, and a PCR screening test is available.