INHERITANCE OF HISTIOCYTOSIS IN BERNESE MOUNTAIN DOGS

One hundred and twenty-seven cases of histiocytosis in Bernese mountai n dogs (BMD) were evaluated to determine if the tumour is inherited. F amily data ruled out autosomal recessive, autosomal dominant and sex-l inked modes of inheritance. The trait was determined to be inherited w ith a polygenic mode of inheritance. The salient points permitting thi s conclusion are: pedigrees developed from independently selected prop ositi link up allowing the tracing of all cases through several genera tions; multiple cases occur in the same litter; multiple cases have be en produced by given darns and sires; there is a higher frequency of t he disease among offspring of affected parents when compared to offspr ing of normal parents that produced histiocytosis and all offspring in the general population of BMDs; the fact that histiocytosis is common in BMDs and rare in eight other breeds and accounts for 25.4 per cent of the 500 tumours studied in this breed. The heritability of this tr ait was calculated to be 0.298.