Hi, this is Tom, and in this episode I'm going to be going through spinal muscular atrophy.

And you can find notes at zero to finals.com slash SMA and in the zero to finals pediatrics book.

And you can find flashcards and questions at members.0.0.0.com.

So let's jump straight in.

Spinal muscular atrophy, or SMA, is a rare autosomal recessive condition caused by deletion or

mutation of the SMN1 gene, leading to deficiency of the survival motor neuron

or SMN protein. It causes a progressive loss of motor neurons, causing progressive

muscular weakness. Let's talk about the presentation.

Spinal muscular atrophy affects the lower motor neurons in the spinal cord. This means there

will be lower motor neuron signs, such as vesiculations, reduced muscle bulk, reduced tone, reduced power, and reduced

or absent reflexes.

Let's talk about the categories.

There are four categories of spinal muscular atrophy that are numbered from most to least severe.

SMA type 1 has an onset in the first few months of life.

Previously, it would progress to death within two years.

However, new genetic therapies have extended life expectancy beyond two years.

SMA type 2 has an onset in the first 18 months.

Most patients never walk but survive into adulthood.

SMA type 3 has an onset after the first year of life.

Most walk without support but subsequently lose that ability. Respiratory muscles are less affected and life expectancy is close to normal.

SMA type 4 has an onset in the patient's 20s. Most will retain the ability to walk short distances

but may require a wheelchair for mobility. Everyday tasks can lead to significant fatigue.

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