Image caption Caoilte Fitzsimons, who is three years of age, has the severest form of SMA

The families of three NI children who have Spinal Muscular Atrophy (SMA) are calling on the Belfast Health Trust to explain why they are being denied access to what they say is a potentially life-changing drug.

SMA is a genetic disease that affects motor neurones, causing progressive muscle weakness and loss of movement.

The new drug, Nusinersen, was approved in December but has yet to be licensed.

The trust has said the administration of the drug is complex.

It said it requires highly skilled clinicians with access to theatres as well as other limited resources. It said all of these posed challenges to the health service. Only three children in Northern Ireland have the severest form of the condition, SMA type one.

A fourth child who has SMA type two is also potentially eligible, however only one child has started the treatment.

As it has yet to be licensed, Nusinersen is provided free from the pharmaceutical company.

It is administered via a lumbar puncture which means it is injected into the spine.

Three-year-old Caoilte Fitzsimons has the severest form of SMA and is unable to sit, walk, crawl, feed, breathe or hold her head without support.

Her mum, Fiona, told the BBC that the family want answers.

"There are only four children with the condition - why is one getting this treatment and the others are not?

"We are so angry we feel our children are being neglected."

The children, three girls and a boy are all aged between one and six years of age.

Image caption Caoilte's mother Fiona said the family want answers

Steven Boobyer's daughter, Mia, is six.

"No one is talking to us directly," he said.

"There has been a delay they seem to be putting it down to funding. We don't know what is going on, whether it's political, we aren't being given straight answers.

"It's terrible, you see Mia today and she is doing so well for what she has and every day we have to look at her wee face and think that one day she will get what she deserves."

In an email seen by the BBC, the Boobyer family are told that cost is an issue.

The doctor who wrote the email is quoted as saying that as well as an anaesthetist, a nurse and doctor theatre space would also be required.

They add that while they understand Nusinersen "would be free up until the point it gets its licence - the ongoing cost will be huge and the Children's hospital staff can't make that decision".

Image caption Steven Boobyer said no-one was talking directly to his family about the matter

They are "also slightly unsure whether the current instability at Stormont could mean such approval decisions would be delayed".

There was no form of treatment for SMA until 23 December 2016.

The American Food and Drug Agency then announced that it had given full approval for the first treatment for the condition with Nusinersen.

While approval for a licence is yet to be made available, an arrangement called the Extended Access Programme allows children who are judged eligible to be given the drug. Belfast was included as one of the places where the drug had been made available.

'Need it urgently'

According to the families they discovered this information via an SMA website.

They are also angry that in the New Year they learned by chance that one child had started the treatment.

Noah Collins is two years old. He has also been diagnosed with SMA type one.

His mother, Rachel, told BBC News NI that they just want an explanation.

"Now that there is the treatment available for SMA, we desperately need it urgently.

Image copyright Press Eye Image caption Nichola Mallon said she believed the drug should be available to all children with the condition

"SMA is a degenerative muscle wasting condition, therefore we don't have time to spare. The results of this drug have been so positive (in trial in America) our children deserve this treatment."

The SDLP's Nichola Mallon has taken up the issue.

Through an urgent assembly question Ms Mallon has asked the health minister whether she will take steps to ensure that all children in Northern Ireland diagnosed with SMA type one are included in the Nusinersen drug trial.

Ms Mallon said she believed the "drug should be available to all children with the condition".

"All the families want is someone to answer their questions," she said.

"This has to be dealt with quickly as time is vital for these children."