Disease of Kennedy

The disease of Kennedy is a genetic Maladie neuromusculaire of the group of the amyotrophies spinales in connection with a Expansion of the Gène coding the receiver with the androgens. It touches only the boys.

Other names of the disease

  • Amyotrophie bulbo-spinale related to X
  • muscular spinale and bulbar Atrophy
  • SMAX1

Etiology

  • Expansion of the Codon CAG repeated (> 38 CAG) of the Gene AR located at the level of the Locus q11-q12 of the Chromosome X

Incidence

The incidence is of 1 on 50  000 births of boys. This pathology touches the European populations and Asian. It seems little to touch the black populations. The Japanese populations and Scandinavian seem to be more touched by this pathology.

Description

The signs of the disease do not appear before puberty. The teenager presents a late or weak puberty with a gynécomastie and a hypotrophie testiculaire. The muscular weaknesses and the muscular atrophy appear towards the old one 20 years but sometimes not before 50 years.
The first signs are the difficulty with walk or the tendency to falls.
After one or two tens of years of evolution, the difficulty of climbing is manifest. And 1/3 of the individuals at the end of 20 years are in wheelchair
Difficulties with swallowing or elocution testify to the attack of the bulbar risks being able to lead to a death by respiratory Insuffisance (reached diaphragm) especially among patients in wheelchair.
But this Pathologie is seldom threatening and the lifespan is not decreased by this pathology.
Troubles of erection are often described among these patients.

Diagnosis

Private clinic

  • Adolescent presenting a Atrophy testiculaire and/or a Azoospermie with a Gynécomastie
  • Disease of the motor bike neuron with muscular weakness and or of cramps of the members.
  • Disease of the bulbar motor bike neuron with Fasciculation S of the language and the lips.
  • difficult Swallowing
  • Absence of cerebral signs of attack (No hyperreflectivity)
  • family History of disease related to X

Electromyography

Genetics

  • the expansion of repeated triplet CAG (> 38 CAG) of the Gène AR located at the level of the Locus q11-q12 of the Chromosome X makes the diagnosis.
  • the normal number of expansion of the triplet is equal or lower than 34
  • No consensus exists on the significance of an expansion of the triplet between 35 and 37

differential Diagnosis

Mainly with:

Treatment

Mode of transmission

Recessive transmission related to X

The genetic Council

Sources

  • Syndrome of Kennedy AFM
  • Orphanet
  • Canadian Site
  • Online Mendelian Inheritance in Man, OMIM (TM). Johns Hopkins University, Baltimore, MANDELEVIUM. MIM Number: 313200 * Albert R Spada, Spinal and Bulbar Muscular Atrophy In GeneTests: Medical Genetics Information Resource (database online). Copyright, University off Washington, Seattle. 1993-2005
Kennedy

Associations

  • French Association
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