Hair Cycle Arrest in Dogs

Hair cycle arrest is known by many names, but probably the most frequently used by veterinary professionals is the term “Alopecia X”, the name given to a skin condition of unknown origin which is not inflammatory but presents with hair loss.  

Because there are other terms used for this condition, many vets have chosen to refer to this condition as simply HCA (hair cycle arrest) as this describes the process which is ongoing.

Hair cycle arrest is quite simply defined as an interruption in the normal cyclic life of a hair follicle which results in reduced hair on the host.

The symptoms of hair cycle arrest in dogs are what one might expect for the most part - loss of hair.  But the hair loss found in Alopecia X or hair cycle arrest is fairly consistent in its pattern and occurrence of hair loss:

• Condition is defined by non-itchy, progressive hair loss 
• Hair loss occurs initially, followed by development of dull and dry coat (wooly type coat)
• Generally affects the trunk, tail, thighs and other frictional areas of canine
• The skin can become hyperpigmented appearing grey or black
• Hair loss can be complete or partial, retaining the wooly coat

Types 

Hair cycle arrest (HCA) in dogs can fall into three basic categories:

• Systemic diseases -  For example, endocrine system abnormalities which can include thyroid dysfunction and other hormonal abnormalities and skin infections resulting from bacteria, fungi and parasitic attacks
• Hereditary -  These are genetic DNA defects which can cause follicle dysplasias and skin pigmentary abnormalities
• True hair cycle arrest with no systemic underlying cause; canines who suffer from this type are otherwise healthy

The causes of hair cycle arrest in dogs remains unknown, though research continues on an ongoing basis, as veterinary professionals try to understand the hair growth cycle in all species having hair.  There are some systemic underlying conditions which are known to be associated with hair loss in dogs and, as such, will need to be eliminated, ruled out or treated:

• Hypothyroidism
• Cushing’s Syndrome
• Telogen defluxion
• Pattern baldness
• Cyclic flank alopecia
• Post-clipping alopecia

Any of these conditions can have an effect on the loss of hair of which your pet may be suffering.  If your veterinary professional’s examination and subsequent testing finds one of these, or any other underlying systemic condition which he feels is contributing to the hair loss, he will need to treat that condition first.

As noted above, there are no known causes for hair cycle arrest (HCA) in dogs and there are a number of underlying systemic conditions or diseases which are known to cause hair loss in dogs.  In view of this, I’m sure you can see that diagnosing your canine family member’s hair loss is not a “cut and dried” process.  

When your veterinary professional begins his diagnostic process, he will need information from you which will need to cover multiple areas of your pet’s life and home situation.  Some of the conditions known to cause hair loss could emanate from dietary regimens (intolerance and changes), parasitic infestation, exposure to possible allergens as well as bacterial and fungal elements, or even stressful situations. Being prepared to provide information into these areas will help your vet a great deal.

Your vet will do a physical examination of your doggy family member and will likely need to order some blood chemistry panels, thyroid testing, various other tissue samples and scrapings for laboratory review and cultures of blood, tissue, urine and fecal samples.  Depending upon his clinical findings and the results of the testing he has ordered, various modalities of imaging might be in order as well (x-rays, CT scan, MRI imaging).  When all of this information has been assimilated, he will develop and initiate an appropriate treatment plan for your canine family member.

Treatment options to be recommended will be based upon what conditions are felt to be at the root of, or at least contributing, to the hair loss in your dog.  Here are some conditions and their likely treatments which might be contributing or causing the hair loss:

• Castration response alopecia - If this is the cause, a period of recuperation following the neutering or spaying should remedy the problem, though it could take several months and may require additional care to generate hair regrowth
• Growth hormone causes - If this is determined to be, at least in part, the cause for the hair loss, administration of the needed hormones would be the treatment
• Melatonin administered orally - The over-the-counter version has been utilized under strict veterinary supervision for some situations - this is not something you should try on your own but only under the supervision and advice of your attending vet
• Cortisol and sex hormones - If there is an imbalance in this area, administration of the deficient hormones will likely be the recommendation

There is no absolute cure for true hair cycle arrest in dogs (also called Alopecia X) but your veterinary professional may be able to help manage the condition.  If the cause of hair loss in your canine family member is due to an underlying systemic condition, such as any of those noted above, your vet will initiate treatment for that condition, which may help to stem the tide of the hair loss in your dog.

For the most part, conditions which cause hair cycle arrest in dogs is treatable or manageable.  If your canine family member is otherwise healthy, not having been diagnosed with any underlying systemic condition or disease, then you can expect your pet to have a relatively normal lifespan for his breed. You may have to make some adjustments in his overall lifestyle to protect your pet from exposure to the elements which will be greater when he is experiencing hair loss episodes.  This may be as simple as utilizing doggy t-shirts and sweaters or providing extra shade when he is outside.