Pelger-Huet syndrome anomaly and merle genetics
History of Pelger-Huet Anomaly
- abnormality in morphology in white blood cells was first discovered by Pelger in 1928, when studying blood of tuberculosis patients
- Huet found similar morphology in his patients in 1932 and hypothesized that it was genetically linked
- Huet confirmed it was linked to genetics and not to tuberculosis, also that the abnormality was benign
- The term for this abnormality was changed from Pelger anomaly to Pelger-Huet anomaly
Pelger-Huet: Who is affected? What is affected?
- Affects: Humans, Rabbits, Cats, Dogs, Horses, and Mice
- Affects other breeds: Cocker Spanials, Basenji's, Border Collie's, etc.
- Occurs approximately 9.8% in Australian Shepherds
- Affects white blood cells
mode of inheritance, diagnosis, and prognosis
- Autosomal dominant, incomplete penetrance
- It can be congenital or pseudo (acquired via disease/ infection)
- Benign for heterozygous; lethal for homozygous (reabsorbed in Utero)
- Morphological differences between Hetero and Homozygous P-H anomaly were discovered in rabbits
- Homozygous is incredibly rare in dogs, but few cases suggest it can lead to skeletal deformities (known cases in Samoyed breed)
- Phenotypic in the blood, affecting granulocytes; PHA changes the morphology in Neutrophils (white blood cells)
- Nuclei of Neutrophils are hyposegmented and bilobed
- Can be tested using blood smears and staining
Pelger-Huet anomaly affects
- Misconception: P-H was believed to be linked to, associated with, or misdiagnosed as: chronic infection, preleukemic syndrome, inflammation or infection, or drug-induced chances in leucocyte's, left shift ( increase in immature white blood cells, typically an indicator of inflammation or infection)
- Neutrophils with P-H are still functional and effective against bacterial infections
- There is no relation between P-H and risk of disease/ infection
Merle gene- What is Merle? Mode of inheritance?
- Standard merle (Mm): a intermingled mixture of diluted and normal pigments
- Merle dogs can commonly have blue irisis or be heterochromic
- Double merle (MM): predominantly white
- Inherited autosomal, incomplete dominance
- Two locus: Merle (M) and Separate Harlequin (S)
How are Shepherds affected?
- Double merle (aka merle syndrome) can lead to deformities
- Double merle can impaire auditory (deafness) and optic systems
- Microphthalmia- one or both eyeballs look small
- Coloboma- a hole in structure of eye
- Similar to Waardenburg syndrome in humans
Merle Syndrome testing and prevention
- Merle parent can produce non-merle offspring
- Tests can be run for cryptic, and probability calculations for merle vs non-merle offspring
- Can prevent via testing and improved breeding methods
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Science, W. 2015. (Merle) Dog coat. Youtube. Available from: https://www.youtube.com/watch?v=d_mrjdwr7i8. Accessed April 28, 2016.
Vale, André M. , Klívio Loreno R. Tomaz, Rejane S. Sousa, and Benito Soto-Blanco. 2011. Pelger-Huët anomaly in two related mixed-breed dogs. Journal of Veterinary Diagnostic Investigation. 23(4). 863-865. DOI: 10.1177.