Spinal Muscular Atrophy (SMN1)

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What is Spinal Muscular Atrophy?

Spinal muscular atrophy (SMA) is a group of inherited diseases that cause muscle damage (progressive muscle weakness). It is the second leading cause of neuromuscular disease, after Duchenne muscular dystrophy.

Four subtypes have been defined depending on the age of appearance and of the gravity of the disease:
Type I or Werdnig-Hoffman: is the most serious form that appears before 6 months of age
Type II: appears between 6 and 18 months
Type III: starts in childhood and adolescence
Type IV: is even milder, with weakness starting in adulthood

All these subtypes are characterized by a muscular weakness (symmetrical and progressive) and a muscular atrophy of variable gravity.

  • Symptoms in an infant: breathing difficulty, feeding difficulty and poor muscle tone.
  • Symptoms in a child: respiratory infections, posture that gets worse and nasal speech

Infografico Carriers

What is the next step if I’m a carrier of Spinal Muscular Atrophy?

If you are found to be a carrier of Spinal muscular atrophy, it is important that your partner be tested for the same genetic disorder.

 

What if my partner is not a carrier?

If your partner’s test for Spinal muscular atrophy is negative, the chance to have an affected child is low. However there is currently no test able to detect all existing mutations, so there is always a residual risk that the person who has done the test is a carrier of other less frequent mutations.

 

What if both me and my partner are carriers of Spinal Muscular Atrophy?

When both parents are carriers of Spinal muscular atrophy, the probability of having a child with this disease is 25%.

We recommend that you discuss your results with your doctor or genetic counselor in order to know more about reproductive options.

 

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