what is SMA?

Question 1

full form of sma?

Answer 1

Spinal Muscular Atrophy (SMA)

Question 2

what is sma?

Answer 2

Spinal Muscular Atrophy (SMA) is a genetic condition under the scope of the neurodegenerative disorders and Motor Neurone Disease MND. It is characterised by degeneration of alpha motor neurons in the spinal cord that affects the control of voluntary muscle movement.

Question 3

epidemiology?

Answer 3

The disease is characterised as an autosomal recessive condition with prevalence of approximate 1 in 6-10,000 births affected by SMA with a carrier frequency of 1 in 35-70

Question 4

Classification of SMA type?

Answer 4

depends on the age of onset and the highest level of motor function achieved

SMA type I (Werdnig-Hoffmann disease) - affects babies less than six months old and is the most severe type of the disease. Sitting unsupported may never be achieved. Present with profound hypotonia, symmetrical flaccid paralysis, and no head control with poor spontaneous mobility and reduced antigravity movements of limbs.

SMA type II - develops in babies between 7 and 18 months old. This type is less severe than type I and most children survive into adulthood and can live long, fulfilling lives. May achieve ability to sit unsupported but may not be able to walk independently. Joint contractures and kyphoscoliosis are very common along with fine tremors of upper extremities.

SMA type III (Kugelberg-Welander disease) - appears after 18 months of age and is the least severe type affecting children. SMA type III has been divided into two further sub-categories: SMA IIIa and SMA IIIb - according to the time when the first symptoms of the condition appears (if before or after 3 years of age).

SMA type IV - this type of SMA patients are diagnosed in adulthood and they present with only mild problems.

Question 5

Clinical Presentation and Classification?

Answer 5

Spinal Muscular Atrophy (SMA) is the second most common neuromuscular disorder of childhood. People affected by the mildest types of SMA have proximal weakness and impaired ambulation. Furthermore, fatigue is a symptom to present in almost every case of SMA which may also lead to impaired function and endurance. Current research in the area shows that there is good correlation between upper and lower limb function in patients with the disease. There are several types of SMA, which start at different ages and may present with various phenotype

Question 6

Clinically Relevant Anatomy

Answer 6

SMA is caused by deficiency of a motor neuron protein called SMN (Survival Motor Neuron). This protein is essential for normal motor function and the lack of it is caused by genetic flaws on chromosome 5 in the gene SMN1. The neighbouring SMN2 gene can compensate some of the functions of SMN1 and this is where some of the pharmaceutical companies trying to develop a drug which can enhance the effect of SMN2.

Question 7

Pathological Process

Answer 7

Spinal Muscular Atrophy is an autosomal recessive condition due in most cases to the homozygous deletion of the SMN1 gene[3]. This means that both parents of the affected individual are only carriers of the affected gene. Therefore, they are not going to present with any symptoms of the disease and this is what makes SMA difficult to foreseen and apply preventable measures.