JPC SYSTEMIC PATHOLOGY
Musculoskeletal System
March 2019
M-M13 (NP)

Signalment (JPC #75-10):  Neonatal Chester white piglet

HISTORY:  Six littermates of this piglet were stillborn and 6 more died within a few hours of birth.  Remaining piglets, including this one, were unable to stand or adduct their hind legs, which extended forward and laterally (“splay legged”).  Foreleg involvement was also seen in some piglets.  Gross lesions were not evident at necropsy.

MICROSCOPIC DESCRIPTION:  Skeletal muscle:  Diffusely myofibers are irregularly sized and contain decreased numbers of myofibrils that are aggregated centrally or eccentrically and surrounded by clear space.  Diffusely, myocytes are pale, lack cross-striations and frequently have large nuclei with vesiculate chromatin.

MORPHOLOGIC DIAGNOSIS:  Skeletal muscle:  Myofibrillar hypoplasia, diffuse, moderate, Chester white, porcine.

CONDITION:  Myofibrillar hypoplasia

SYNONYMS:  Splayleg, spraddle-leg

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL MICROSCOPIC FINDINGS:

ULTRASTRUCTURE:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Cooper BJ, Valentine BA. Muscle and Tendon. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St Louis, MO: Elsevier; 2016: 189-190.
  2. Dewey CE. Diseases of the nervous and locomotor systems. In: Straw BE, Zimmerman JJ, D'Allaire S, Taylor DJ, eds. Diseases of Swine. 9th ed. Ames, IA: Blackwell Publishing; 2006:88.
  3. Olson EJ, Carlson CS. Bones, Joints, Tendons, and Ligaments. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:945.
  4. Radostits OM, Gay CC, Blood DC, Hinchcliff KW. Veterinary Medicine, a Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses. 9th ed. Philadelphia, PA: W B Saunders; 2000:1800-1801.
  5. Seehusen F, Hahn K, Herder V, Weigand M, Habierski A, Gerhauser I, Wohlsein P, Peters M, Varela M, Palmarini M, Baumgärtner W. Skeletal muscle hypoplasia represents the only significant lesion in peripheral organs of ruminants infected with Schmallenberg virus during gestation. J Comp Pathol. 2014; 151(2-3):148-52.


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