Breed

Common Clinical Signs (in roughly decreasing order)

CK/AST

Draft-related

Abnormal hind limb gait

Poor muscling, either rump and topline or generalized

Poor performance/lack of energy

Exercise intolerance

Severe “tying up” (“Monday Morning Disease”)

Inability to rise after laying down

Episodic “colic”

Usually normal to slightly increased.

Markedly increased associated with severe rhabdomyolysis

AST >500 U/L is suggestive of EPSM

Quarter horse – related

“Tying up”

Abnormal hind limb gait

Attitude problems under saddle

Poor performance/lack of energy

Back soreness

Episodic “colic”

Generalized muscle atrophy

Can be very high in horses that “tie up,”especially when obtained 4-6 hours after exercise.

Will be normal or only slightly increased in horses with other problems.

Warmblood

Poor performance/lack of energy

Attitude problems under saddle

Back soreness

Abnormal hind limb gait

“Tying up”

Episodic “colic”

As for Quarter horse-related

Arabian

“Tying up”

Poor performance/lack of energy

Abnormal hind limb gait

As for Quarter horse-related

Thoroughbred and Standardbred

“Tying up”

Poor muscling/generalized muscle atrophy

Abnormal hind limb gait

Attitude problems under saddle (TB)

As for Quarter horse-related

American miniature (young adults)

Poor muscling

Lack of energy

Persistent mild to moderate increase

Icelandic pony

Lack of energy

Stiff/abnormal gait

Poor performance

“Tying up”

Often mild to moderate increase

Other breeds

Any or all of the above

Any or all of the above