Case A
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History
A two-month-old Saanen kid, one of three with a history of lameness, recumbency and swollen joints. At necropsy, joints had villous proliferation of the synovium and a suppurative exudate. Mammary tissue was swollen and congested with a suppurative exudate on the cut surface.
Example histopathological description
The section consists of haired skin, underlying subcutis and mammary gland. There are multiple profiles of markedly dilated mammary ducts whose lumens are filled with large amounts of necrosuppurative exudate. Small amounts of fine, scattered mineral deposition is present within components of the exudate. Ductal epithelium is absent to severely attenuated. Beneath the epithelium there is a band of foamy macrophages. The inflammation spills irregularly into the periductular parenchyma, remaining predominately centred on ducts, with mild to moderately severe multifocal to coalescing areas of lymphoplasmacytic inflammation and multiple lymphofollicular aggregates. There is mild periductular fibroplasia and fibrosis with a small amount of collagen deposition. The parenchyma is mildly oedematous and lymphatics are diffusely dilated. There is pronounced diffuse hyperaemia of the tissues. No infectious agent is identifiable in this H&E-stained section.
Morphological diagnosis
Mastitis, suppurative, subacute, diffuse, moderately severe, with interstitial lymphoplasmacytic accumulations
Aetiological diagnosis
This was a case of mycoplasmosis with Mycoplasma capricolum isolated from joints and mammary tissue.
Differential diagnoses
- Mycoplasma mastitis (contagious agalactia)
- CAE with concurrent non-specific bacterial ductal mastitis
- Chronic non-specific bacterial mastitis (Pasteurella sp, Staphylococcus sp, Streptococcussp)
Case B
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History
A six-year-old thoroughbred horse, on recovery from anaesthetic for minor surgery, developed hyperthermia, tachycardia, hyperpnoea, muscle rigidity and died.
Example histopathological description
The section consists of a 25 x 20 x 12 mm piece of skeletal muscle with multiple fascicles containing transversely, obliquely and longitudinally sectioned myofibres. Numerous muscle fibres show acute segmental necrosis with swelling, loss of identifiable cross striations, hyalinisation or eosinophilic coagulation of the sarcoplasm and pronounced hypercontraction band formation. In many areas myofibres are devoid of cytoplasm or contain small amounts of eosinophilic, floccular debris within collapsed endomysial outlines. Occasional fibres have acute swelling of myofibre and satellite cell nuclei. The lightly basophilic, finely granular appearance of some degenerate areas of sarcoplasm suggests mild mineralisation. There is mild diffuse interstitial oedema. All lesions are of comparable age, there is negligible evidence of myofibre phagocytosis.
Morphological diagnosis
Rhabdomyolysis, segmental, acute, generalised, severe
Aetiological diagnosis
This was a case of post-anaesthetic myopathy
Differential diagnosis
- Post-anaesthetic myopathy
- Malignant hyperthermia
- Equine polysaccharide storage myopathy
- Nutritional and toxic myopathies
- Exertional rhabdomyolysis
- Hyperkalaemic periodic paralysis