Acral mutilation syndrome

From Dog
Histological appearance of a ganglion from a dog with AMS, showing reduced packing of nerve cell bodies and widened interstitial areas in subcapsular region of cervical ganglion[1]

Acral mutilation syndrome (AMS) is a rare autosomal-recessive genetic sensory neuropathy of dogs that results in progressive mutilation of the distal extremities[2].

This disease is a variant form of polyneuropathy, similar to ganglioradiculitis, and is characterized by a sensory (afferent) neuropathy in the limbs (stocking-glove sensory loss), and is dissimilar to acral lick dermatitis, which is an obsessive-compulsive disorder of dogs.

AMS results in arrested development of primary sensory neurons followed by progressive postnatal degeneration, with similar neuropathology as is witnessed with Navajo neurohepatopathy[3] in humans.

This disease has been reported in Miniature Schnauzers, German Short-Haired Pointers, English Pointers, English Springer Spaniels and French Spaniels[4].

Clinically affected dogs present with overgrooming and licking of pads and paws to the point of excoriations, ulceration and bleeding. These dogs may be identified soon after birth by their lack of response to acral pinprick or compression. Affected pups are often smaller than unaffected littermates and owners report the pup licking and biting at their paws.

Auto-amputation of claws, digits and footpads occurs in severe cases, with acral changes including swollen reddened paws, paronychia, palmar and plantar ulceration, nail loss and painless fractures.

Neurological examination usually reveals acral analgesia with a variable proximal extent. Tendon reflexes remain intact. Signs of proprioceptive, somatic motor or autonomic impairment have not been observed[1].

In dogs, single or multiple feet can be affected and affected animals can walk on their severely mutilated feet without evidence of pain, lameness, or ataxia[5].

Diagnosis is usually based on nerve biopsies taken under general anesthesia or at postmortem. Reduction in size of the spinal ganglia is observed grossly at necropsy.

A differential diagnosis would include canine distemper virus and other sensory neuropathies such as ganglioradiculitis.

Mild affected dogs can be treated with anxiolytic drugs such as diazepam and elizabethan collars, but many cases rapidly deteriorate, requiring euthanasia due to deteriorating quality of life.

References

  1. 1.0 1.1 Cummings JF et al (1983) Hereditary sensory neuropathy. Nociceptive loss and acral mutilation in pointer dogs: canine hereditary sensory neuropathy. Am J Pathol 112(1):136-138
  2. Cummings JF et al (1981) Acral mutilation and nociceptive loss in English Pointer dogs. Acta Neuropathol (Berlin) 53:119-127
  3. Karadimas CL et al (2006) Navajo neurohepatopathy is caused by a mutation in the MPV17 gene. Am J Hum Genet 79(3):544-548
  4. Bardagí M et al (2011) Acral mutilation syndrome in a miniature pinscher. J Comp Pathol 144(2-3):235-238
  5. Paradis M et al (2005) Acral mutilation and analgesia in 13 French spaniels. Vet Dermatol 16(2):87-93