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Orlando Paciello » 6.Congenital and hereditary muscle disorders in farm animals


Congenital and hereditary muscle disorders in farm animals

Many hereditary, congenital or neonatal defects can affect muscles.
Hereditary muscle disorders can be seen at birth or soon afterwards, or can appear years later.
Molecular biology and genetic testing have combined to produce better knowledge of many myopathies in animals and have made it possible to identify affected animals or those who are carriers of genetic disease.

Example of congential arthrogryposis in a calf

Example of congential arthrogryposis in a calf

Example of congenital arthrogryposis in a calf

Example of congenital arthrogryposis in a calf


Innervation defect

  • Congenital lower motor neurone disease leads to serious alterations in the development of muscle fibres.
  • Innervation plays a fundamental role in the development and maturation of myofibres and the muscle lesions which result from a genetic defect affecting the nerves can be serious and complex.
  • The most common example of this type of defect is congenital arthrogryposis
Serious case of bovine arthrogryposis

Serious case of bovine arthrogryposis


Congenital arthrogryposis

This refers to persistent flexion of a joint because of muscle spasm or retraction, or because of intra and extracapsular ankylosis.
CAR = Congenital articular rigidity which is seen in lambs, calves, foals and piglets falls into the category of malformation of the joints or muscular aplasia or hypoplasia.
It is characterised by stiffness of single or multiple joints (arthrogryposis multiplex congenita), is non-progressive, is caused by alterations to the nervous system and is often associated with skeletal malformation.

Congenital arachnomelia and arthrogryposis in a cow

Congenital arachnomelia and arthrogryposis in a cow


Congenital arthrogryposis  (cont.)

The muscle groups in the affected joints are hypoplastic, i.e. the muscles are not fully developed and muscle tissue is replaced by adipose and fibrous tissue. In bovines, the disease occurs in different breeds but especially in:

  • Shorthorn;
  • Charolais;
  • Piemontese;
  • Swedish dole;
  • Merino and corriedale sheep;
  • Norwegian fjord horses.
Example of deformed extremities in a calf

Example of deformed extremities in a calf

Example of deformed extremities in a calf

Example of deformed extremities in a calf


Congenital myofibrillar hypoplasia (splayleg)

The most significant congenital defect in intensively reared swine (pietrain, landrace and large White).
There is congenital myofibrillar hypoplasia which leads to muscle weakness in the hind quarters and less frequently in the front making it difficult for the animal to stand. The limbs are held in abduction, like a sitting down dog with limbs outstretched and splayed.

Serious weakness of hind quarters with a “sitting dog” appearance

Serious weakness of hind quarters with a "sitting dog" appearance


Congenital myofibrillar hypoplasia (splayleg)

The etiology of this disease is believed to be multi-factorial. Factors to do with food, toxins or environment probably combine with a hereditary predisposition.

It has been noted that incidence of the disease increases with episodes of PRRS (Porcine reproductive respiratory syndrome).

Serious hind quarter weakness in young pig

Serious hind quarter weakness in young pig

Methods adopted for postural correction

Methods adopted for postural correction


Diaphragmatic myopathy in Meuse-Rhine-Yssel cattle

  • Seen in bovines of the Meuse-Rhine-Yssel breed. Affects mainly diaphragm and intercostal muscles. Age varies from 2-10 years with an average of 5.
  • The muscles appear pale, swollen and rigid.
An example of Meuse-Rhine-Yssel cattle breed

An example of Meuse-Rhine-Yssel cattle breed


Progressive congenital myopathy in ovines

  • With the Merino breed of sheep there is a well-known progressivecongenital myopathy which reveals itself in stunted growth and progressive difficulty with flexion of the posterior limbs from 3-4 weeks of age onwards. The animals die in first 6-18 months of life as the dystrophy gradually worsens.
  • The muscles look hard and grey-coloured.
Serious weakness in a sheep

Serious weakness in a sheep


Spider Lamb Syndrome ( Hereditary Chondrodysplasia )

A genetic disease characterized by skeletal deformity in young lambs. It is a recessive hereditary disorder.

This means that any lambs with the disease received a recessive gene from both parents.

This disease is seen mainly in black-faced lambs.

  • 75% Suffolk
  • 25% Hampshire
Example of skeletal deformity in young lamb

Example of skeletal deformity in young lamb

Example of skeletal deformity in young lamb

Example of skeletal deformity in young lamb


Flexor deformity in foals

Flexor deformity is a pathologic condition affecting the joints, characterized by deviation in the sagittal plane and persistent hyperflexion in one articular region, resulting in altered biomechanics of the joint.
The most frequent sites for this kind of deformity are:
metacarpal / tarsal phalangeal and carpal joints, and more rarely the distal interphalangeal joints, tarsals or vertebral column.

Photo by kind permission of prof.ssa M.P. Pasolini

Photo by kind permission of prof.ssa M.P. Pasolini


Etiology

Congenital flexor deformity is believed to be the result of a defective positioning of the fetus in the uterus.

However, various hypotheses have been put forward, including:

  • the action of toxic or infective agents during pregnancy;
  • endocrine factors (hypothyroidism);
  • neuromuscular pathologies.

Flexor deformity in foals (cont.)

In foals, as in children, symptoms like “flexor deformity” and “hypotonia and/or muscle weakness” may be the expression of congenital neuromuscular pathologies.

Photo by kind permission of prof.ssa M.P. Pasolini

Photo by kind permission of prof.ssa M.P. Pasolini


Causes of flexor deformity in children

In children, many congenital myopathies present with flexor deformity, muscle hypotonia, reduction of visus and difficulty feeding.

Congenital myopathies present typical morphological changes which show up on histochemical tests.
They are often associated with a predominance or hypotrophy of type I fibres.

Examples of deformities in the extremities of a baby. This kind of anatomical-clinical picture is very similar to the congenital changes seen in young animals

Examples of deformities in the extremities of a baby. This kind of anatomical-clinical picture is very similar to the congenital changes seen in young animals


Most-frequently encountered congenital myopathies

  • Central Core Disease (CCD)
  • Nemalinic myopathy
  • Myotubular myopathy
  • Desmin Myopathy
  • Fibre type disproportion myopathy
  • Cytoplasmic body myopathy

Central Core Disease (CCD)

  • The first Congenital Myopathy to be discovered (1956).
  • Congenital hypotonia, muscle weakness and flexor deformity are the main symptoms
  • Histologically it is characterised by well-defined rounded areas (cores) inside the type I fibres.
  • Cores look like areas without mitochondrial activity and with oxidative insufficiency.
Foal affected by serious articular rigidity and deformity of distal extremity of limb

Foal affected by serious articular rigidity and deformity of distal extremity of limb

Histological tests using histoenzymatic stains revealed typical empty areas at the centre of the muscle fibre

Histological tests using histoenzymatic stains revealed typical empty areas at the centre of the muscle fibre


Nemalinic Myopathy

Congenital, non-progressive myopathy, characterised by small subsarcolemma rod structures between the myofibrils.
These structures correspond to the Z band and are continuous with actin filaments.
Congenital hypotonia, generalized muscle weakness, alterations to facial musculature and accompanying palatoschisis with relevant clinical symptoms.

Hypertrophic nuclei in the centre of the muscle fibre. Source: Neuromuscolar

Hypertrophic nuclei in the centre of the muscle fibre. Source: Neuromuscolar


Myotubular Myopathy

Myotubular myopathy is perhaps the most serious congenital muscle pathology.
Predominant clinical symptoms are serious hypotonia, insufficiency in spontaneous movement, contracture in neck muscles, multiple flexor deformity and cardiac and respiratory insufficiency.
Histologically the myofibres sometimes appear undifferentiated and similar to those of muscle fibres at the fetal stage.
A transparent halo can be seen around the nuclei, which demonstrates intense oxidative enzyme activity.


Desminic myopathy

A protein accumulation myopathy, which is indicative of a defect in protein catabolism.
Areas of desmina deposits show a lack of oxidative and ATPase activity. The amorphous material can form spheroid aggregates or widespread filaments within the sarcoplasm.
New-borns present with generalized muscle-weakness and cardiomyopathies as well as flexor deformity.

Some fibres appear hyperchromic in histological section with Engel’s trichrome. Source: Neuromuscolar

Some fibres appear hyperchromic in histological section with Engel's trichrome. Source: Neuromuscolar

Some fibres appear hyperchromic in histological sections with Engel’s trichrome. Source: Neuromuscolar

Some fibres appear hyperchromic in histological sections with Engel's trichrome. Source: Neuromuscolar


Fibre type diproportion

Pathology present at birth, characterized by a prevalence (> 12%) and congenital hypotrophy of type I muscle fibres.

Predominant symptoms are muscle weakness, delayed neuromuscular transmission, muscle contractures and respiratory difficulty.

Groups of type I fibres which are uniformly smaller than type II fibres (ATPase ph 4.3)

Groups of type I fibres which are uniformly smaller than type II fibres (ATPase ph 4.3)

Diametric measurements of type 1 and 2 fibres 
Groups of type I fibres uniformly smaller than type II fibres (ATPase ph 4.3)

Diametric measurements of type 1 and 2 fibres Groups of type I fibres uniformly smaller than type II fibres (ATPase ph 4.3)


Flexor deformity in foals

  • Flexor deformity is a symptom which is common to various pathologies so a specific diagnostic path needs to be followed.
  • As in Human Medicine, when a patient presents with flexor deformity, congenital neuromuscular pathology must be considered.
  • Identifying one of these disorders is very interesting because they are hereditary myopathies, and knowing more about them helps to prevent transmission.

Conclusion

We advise you to consult the neuromuscular pathology laboratory at Federico II University in Naples.

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