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May-Hegglin Anomaly Pug Dog Type (MHA)
| Acronym: | MHA |
| Gene: | MYH9 |
| Mutation: | c.5521G>A |
| Inheritance: | Autosomal dominant |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
May-Hegglin Anomaly Pug Dog type (MHA) is a hereditary blood disorder reported until now only in the Pug dog breed. May-Hegglin anomaly belongs to a group of disorders known as thrombocytopenia, a medical condition characterized by low blood platelet count in affected animals. Except in pugs, the May Hegglin anomaly is affecting also human beings. It is named after German physician Richard May and Swiss physician Robert Hegglin. Platelets, or thrombocytes, have a key role in bleeding prevention through the clumping of blood vessel injuries. Platelets are produced in the bone marrow and then released into the bloodstream. At a site of vascular injury, platelets are exposed to the surface which is not from a blood vessel, and they initiate to aggregate with each other, which results in the formation of a hemostatic plug that will seal the defect.
In May-Hegglin anomaly affected pugs, platelets appear to be bigger and their count lower than normal. Changes in neutrophils have been observed as well. The disorder may cause prolonged bleeding time and bruising, which can cause problems post-operation. Other than that, no additional clinical signs are usually observed. In human patients, renal disease, hearing problems, and cataracts are common, but these symptoms have not been reported in Pugs. Usually, the May Hegglin anomaly requires no treatment, except in extreme cases when platelet transfusions may be necessary. May-Hegglin anomaly pug type (MHA) is caused by mutation of the MYH9 gene. The disorder is inherited as an autosomal dominant trait. It is needed one copy of the mutated gene for a dog to develop symptoms. When mating a healthy, unaffected dog with a heterozygous affected dog, chances are 50% that the cub will be affected as well. The disorder equally affects both female and male dogs.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
AFFECTED HETEROZYGOTE |
Tested mutation was detected in animal with „affected heterozygote“ result. Animal tested as affected heterozygote has one wild-type and one mutation allele, it is in heterozygous state. It is likely to develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
**Penetrance of tested mutation, and potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Flatland B, Fry MM, Baek SJ, Bahn JH, LeBlanc CJ, Dunlap JR, Carroll RC, Kosiba DJ, Millsaps DJ, Schleis SE. May-Hegglin anomaly in a dog. Vet Clin Pathol. 2011 Jun; 40(2):207-14.