Hereditary polyneuropathy in the Alaskan Malamute^[*]

Summary

Objective: To prove the hypothesis that a polyneuropathy in Alaskan Malamutes has a genetic background. Material and methods: Pedigrees of 131 related Alaskan Malamutes were included in the current study. Neurological examination, electrodiagnosis as well as muscle and nerve biopsies could be performed in 10 dogs. Information about the disease status of the other 121 Alaskan Malamutes were supplied by referring veterinarians, breeders and owners. Segregation analysis using four different models (monogenic, polygenic, mixed monogenicpolygenic and the phenotypic model) was performed on 71 dogs to test the different mechanisms of genetic transmission. Results: In seven clinically affected dogs abnormal electromyographic findings and reduced nerve conduction velocity were detected. Suspected diagnosis of polyneuropathy was confirmed by nerve biopsy results, characterized by axonal degeneration and hypomyelination. Muscle specimens revealed signs of neurogenic myopathy. Three related clinically normal Alaskan Malamutes also displayed moderate neuromuscular changes in histopathology. In the segregation analysis the polygenic model proved as best suitable to explain the observed segregation pattern among all other models tested. Conclusion: The current study could demonstrate that polyneuropathy in Alaskan Malamutes is a hereditary disease with variable phenotypic expression ranging from severely affected to subclinical forms, which has to be considered in future gene analysis studies.

Zusammenfassung

Ziel der Untersuchung war die Überprüfung der Hypothese, dass die Polyneuropathie des Alaskan Malamute eine erbliche Komponente hat. Material und Methoden: Um diese Hypothese zu bestätigen, wurden Abstammungsnachweise von 131 verwandten Alaskan Malamutes herangezogen. Bei 10 Hunden waren eine neurologische Untersuchung, Elektrodiagnostik und Beurteilung von Nervenund Muskelbioptaten möglich. Weitere Informationen über den Gesundheitsstatus von 121 Alaskan Malamutes konnten über Haustierärzte, Züchter und Besitzer eingeholt werden. Zur Testung der verschiedenen Mechanismen eines Erbgangs wurde bei 71 Hunden eine Segregationsanalyse durchgeführt, die vier Modelle (monogen, polygen, gemischt monogen-polygen und phänotypische Verteilung) beinhaltete. Ergebnisse: Bei sieben erkrankten Alaskan Malamutes ließen sich Spontanaktivität im Elektromyogramm und eine erniedrigte Nervenleitgeschwindigkeit nachweisen. Die histologische Untersuchung von Muskelund Nervbioptaten bestätigte die Verdachtsdiagnose einer Polyneuropathie. Diagnostiziert wurden eine neurogene Muskelatrophie, Axondegeneration und Hypomyelinogenese. Drei verwandte, zum Zeitpunkt der Untersuchung klinisch unauffällige Hunde wiesen histopathologisch ebenfalls geringgradige neuromuskuläre Veränderungen auf. Das polygene Modell der Segregationsanalyse konnte das beobachtete Segregationsmuster am besten erklären. Schlussfolgerung: Es ließ sich zeigen, dass es sich bei der Polyneuropathie des Alaskan Malamute um eine genetische Erkrankung handelt. Der Phänotyp ist sehr variabel und reicht von Tetraparesen bis zu subklinischen Formen. Diese subklinischen Formen müssen bei zukünftigen Genanalysen berücksichtigt werden.

Key words

Dog - electrodiagnosis - muscleand nerve biopsy - segregation analysis

Schlüsselwörter

Hund - Elektrodiagnostik - Muskelund Nervbiopsie - Segregationsanalyse

^* Dedicated to the 60th birthday of Prof. Dr. Ingo Nolte.

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