11 doctors weighed in:

What are the genetics of sma?

11 doctors weighed in
Dr. Richard Roberts
Clinical Genetics
4 doctors agree

In brief: More than one type

Spinal muscular atrophy of infants, before the gene was identified, was called Werdnig-Hoffman disease.
Pitiful-we always looked at the tongues of floppy babies hoping it wasn't fasciculating. No treatment, breathing muscles progressively weakened, resulting in suffocation. 1 chance in 4 of recurrence-maybe. 2% were mew mutations. Kugleberg-Weilander disease had onset after 12 mo. Now 7 forms

In brief: More than one type

Spinal muscular atrophy of infants, before the gene was identified, was called Werdnig-Hoffman disease.
Pitiful-we always looked at the tongues of floppy babies hoping it wasn't fasciculating. No treatment, breathing muscles progressively weakened, resulting in suffocation. 1 chance in 4 of recurrence-maybe. 2% were mew mutations. Kugleberg-Weilander disease had onset after 12 mo. Now 7 forms
Dr. Richard Roberts
Dr. Richard Roberts
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4 comments
Dr. Richard Roberts
The genetics is appallingly complex. In 1/50 of SMA-1, a spontaneous mutation is the cause, not found in a parent, and future sibs are not at risk. 3 forms are prenatal with death before or shortly after delivery. The genetics must be sorted out and appropriate genetic counseling given. Once identified, preimplantation diagnosis is possible. The 7 forms vary in age of onset, 7 being adult onset.
Dr. Richard Roberts
The genetics is appallingly complex. In 1 in 50 of SMA-1, a spontaneous mutation is the cause, not found in a parent, and future sibs are not at risk. 3 forms are prenatal with death before or shortly after delivery. The genetics must be sorted out and appropriate genetic counseling given. Once identified, preimplantation diagnosis is possible. The 7 forms vary in age of onset, 7 being adult.
Holly Barth
General Practice
2 doctors agree

In brief: Autosomal recessive

A defect in the smn1 gene is what is inherited.
Someone has to get 2 copies of this defective gene (one from mom and one from dad) to have sma. If someone only has one copy of the defective-they are a carrier and can pass on that gene to their offspring.

In brief: Autosomal recessive

A defect in the smn1 gene is what is inherited.
Someone has to get 2 copies of this defective gene (one from mom and one from dad) to have sma. If someone only has one copy of the defective-they are a carrier and can pass on that gene to their offspring.
Holly Barth
Holly Barth
Answer assisted by Holly Barth, Medical Student
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Dr. Claudia Mikail
Preventive Medicine
1 doctor agrees

In brief: Spinal muscular atro

There are different forms of spinal muscular atrophy (SMA), which can result from mutations in the following genes: SMN1, UBA1, DYNC1H1, and VAPB.
Having added copies of the SMN2 gene may impact the severity of SMA. (NIH, Genetics Home Reference, Spinal Muscular Atrophy)

In brief: Spinal muscular atro

There are different forms of spinal muscular atrophy (SMA), which can result from mutations in the following genes: SMN1, UBA1, DYNC1H1, and VAPB.
Having added copies of the SMN2 gene may impact the severity of SMA. (NIH, Genetics Home Reference, Spinal Muscular Atrophy)
Dr. Claudia Mikail
Dr. Claudia Mikail
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Dr. Diane Minich
Family Medicine

In brief: SMA

Spinal muscular atrophy (sma) is an autosomal recessive disease caused by a genetic defect in the smn1 gene that codes smn, a protein widely expressed in all eukaryotic cells.
The overall incidence of sma, of all types and across all ethnic groups, is in the range of 1 per 10, 000 individuals; the gene frequency is thus around 1:100, therefore, approximately one in 50 persons are carriers.

In brief: SMA

Spinal muscular atrophy (sma) is an autosomal recessive disease caused by a genetic defect in the smn1 gene that codes smn, a protein widely expressed in all eukaryotic cells.
The overall incidence of sma, of all types and across all ethnic groups, is in the range of 1 per 10, 000 individuals; the gene frequency is thus around 1:100, therefore, approximately one in 50 persons are carriers.
Dr. Diane Minich
Dr. Diane Minich
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