Rugby legend Doddie Weir has called for all motor neurone disease patients to be added to the list of those especially vulnerable to coronavirus.
The former Scotland and Lions star, who revealed his diagnosis in 2017, said those battling the disease needed "help [to] stay alive as long as possible".
But officials said that whether MND patients are on the list depends on their individual circumstances.
Patients are being considered on a case by case basis by their medical teams.
Vulnerable people with certain underlying medical conditions are considered most at risk of severe illness if they catch Covid-19.
They have been sent letters from the chief medical officer asking them asked to stay at home for 12 weeks and minimise contact with other members of their household. It is called "shielding".
They are also offered a weekly delivery of basic groceries and medication, as well as other support services.
But people with MND are not automatically included in this group.
Addressing the UK government's health secretary, Matt Hancock, in a video posted on Twitter, Mr Weir said: "Firstly, I'd like to thank you, your team and all at the NHS and everyone else involved in trying to fight the coronavirus".
But he said that MND is a "terminal illness with horrific short and long-term issues".
"I need your help", he added. "So I ask you; why is MND not on the very vulnerable persons list?
"Would it be possible for you and your team to work with the MND Association and MND Scotland to change this?".
He continues, "People with MND have a hard life in itself never mind trying to fight the coronavirus.
"Please help us stay alive as long as possible. Thank you."
Craig Stockton, MND Scotland's chief executive, said the initial announcement on "shielding" identified six categories of patients considered most at risk from Covid-19.
"The list did not specifically mention those affected by Motor Neurone Disease (MND), yet those affected by this terminal illness often suffer from breathing and respiratory problems, issues which are high risk factors for Covid-19," he added.
He said the Scottish government had taken the additional step of writing to clinicians to ask them to identify which of their patients are considered to be at most risk and should be part of the "shielding" group.
However, because of the nature of MND he said MND Scotland was calling for all those with the disease to be considered as vulnerable and to have access to additional support.
Rigorous rules for shielded group
The UK government's Department of Health said the list of who fell into the clinically extremely vulnerable group and therefore required shielding was continually being refined.
A spokesman said: "Expert doctors have identified specific medical conditions that put someone at greatest risk of severe illness from Covid-19, meaning they're clinically extremely vulnerable and need to shield.
"The list will continue to be reviewed and doctors are identifying additional people who need to shield depending on their individual circumstances.
"Those not in the extremely clinically vulnerable group but who have other underlying medical conditions are still advised to strictly follow our guidance to stay at home and not meet with people outside the household."
Professor Jason Leitch, the Scottish government's national clinical director, said the shielded group was for those who were immunologically compromised, and not all of those with MND were in this category.
He told BBC One Scotland's Coronavirus: Scotland's Response that individual care teams for each patient had been asked to decide if that individual belonged in the vulnerable category.
"Remember that shielded group has got to follow very, very rigorous rules - it's not something we want to do to anybody lightly", he said.
Prof Leitch added that anyone with respiratory symptoms or whose care teams felt they should be on it would be on it.