Familial thyroid follicular cell carcinoma in German Longhaired Pointers

Familial thyroid follicular cell carcinoma (FTFC) is a serious cancer that occurs with increased frequency in German longhaired pointers. The most common clinical symptom is a palpable mass in the neck area, which owners often notice as the first warning sign. Other symptoms of the disease include coughing, hair loss (alopecia), increased urination and thirst (polyuria and polydipsia), and weight loss. The disease begins to manifest relatively early – from the age of four years.

Genetic predisposition plays a significant role in thyroid follicular cell carcinoma. Two serious mutations have been identified in the TPO (thyroid peroxidase) gene, which plays a key role in the synthesis of thyroid hormones, in German long-haired pointers. These are the chr17:800788G>A (p.F686V) and chr17:805276C>T mutations.

The mode of inheritance of the mutations is likely autosomal recessive. The risk of developing FTFC is approximately 16 times higher for dogs carrying two copies of one or both mutations (recessive homozygotes) compared to individuals without these variants. A heterozygote is an individual who has acquired a mutated allele from only one of its parents, is clinically healthy, but can pass the mutated allele on to the offspring. In the case of mating two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% will be carriers, and 25% will inherit the mutated allele from both parents and will have a significantly increased risk of developing this disease.

Genetic testing can clearly reveal an animal's genotype and is a useful tool for breeders to prevent the unintentional breeding of affected puppies.