Skeletal

This is a Skeletal condition.

Hereditary Vitamin D-Resistant Rickets

What is Hereditary Vitamin D-Resistant Rickets?

A disease of insufficient calcium absorption, this can cause lameness and skeletal abnormalities; however, if diagnosed early it can be successfully managed. Calcium absorption occurs at the level of the small intestine and is mediated by calcitriol or Vitamin D. Unlike nutritional rickets, HVDRR is caused by mutations in the Vitamin D Receptor (VDR) leading to poor calcium absorption. However, other than age of onset (nutritional rickets can occur at any time in a dog’s life whereas VDRR tends to affect very young dogs), the two conditions present essentially the same. Symptoms include lameness and skeletal abnormalities, most noticeably an outward bowing of the forelimbs. Due to insufficient amounts of calcium deposition in the bone matrix, dogs are also prone to spontaneous fractures. If left untreated, dogs deteriorate rapidly. Because nutritional rickets is much more common than HVDRR, affected dogs are often incorrectly treated for nutritional rickets to no avail and are often euthanized due to poor response to therapy. Catching HVDRR early can inform appropriate treatment early--however, any skeletal abnormalities that develop prior to treatment are permanent.

What are the signs & symptoms that develop in affected dogs?

Symptoms include lameness and skeletal abnormalities, most noticeably an outward bowing of the forelimbs. Due to insufficient amounts of calcium deposition in the bone matrix, dogs are also prone to spontaneous fractures.

When do signs and symptoms develop?

Signs are first recognized in puppies.

How do vets diagnose this condition?

Genetic testing, clinical signs, radiographs, and laboratory tests are all used to diagnose this condition.

How is this condition treated?

If left untreated, dogs deteriorate rapidly. Because nutritional rickets is much more common than HVDRR, affected dogs are often incorrectly treated for nutritional rickets to no avail and are often euthanized due to poor response to therapy. Catching HVDRR early can inform appropriate treatment. However, any skeletal abnormalities that develop prior to treatment are permanent.

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