Classmates march for Chloe: Marbella schoolgirl with rare disease is only known case in Spain

The 11-year-old, who attends the Marbella Montessori School, is one of just 12 known patients in the world with a condition caused by a mutation of the gene VPS13D – an illness so recently discovered that it does not even have a name yet.

Chloe (pictured) suffers severe muscular pain, especially in her back, hips and legs, and daily cramps, as well as chronic fatigue and having difficulty walking, speaking and swallowing – the latter of which has put her life in danger numerous times.

She has often gone through 'night terrors', although these are currently less frequent, and has attention deficit disorder (ADD) and a visual-perceptive disorder which makes learning and retaining information difficult for her.

Investigation shows that the effects of the VPS13D gene mutation are such that 'the body does not produce enough energy to feed the nervous and muscular system', affecting their 'normal development' and leading to the muscles gradually atrophying irreversibly, according to Dr Matilla and his team at the Germán Trias i Pujol Research Institute (IGTP) in Barcelona.

This means it is essential to find a form of treatment that slows or halts its progression – although until February 2018, all that was known about the VPS13D gene mutation was that it was progressive and incurable and that the effects could not be reversed.

Chloe's condition first raised concerns when she was three, but it was not formally diagnosed until last year.

Marbella Montessori School aims to encourage its pupils to develop empathy, compassion and a sense of community spirit, and their trek from San Pedro Alcántara to Puerto Banús – 5.5 kilometres, ending on the coast – is part of this wider plan.

The children hope to raise as much money as possible for the research project into finding a treatment for the VPS13D gene mutation, since the full cost is expected to be around €200,000.

Given its extreme rarity, the disease and its sufferers need visibility, which the San Pedro-Puerto Banús walk is hoping to generate.

And at least 150 celebrities from all over Spain will be taking part to help raise awareness of Chloe's condition.

In a bid to amass as much funding for the IGTP research project as possible, Chloe's mother has launched a crowdfunding campaign (Gofundme.com/proyecto-chloe-cocofishgo), and the site Investigacionparachloe.org gives information on her condition.

Anyone can join the San Pedro-Puerto Banús walk, whether or not they are linked to the Marbella Montessori School – or to help out in any other way, they can contact the centre's Ann-Marie Garrett on 952 88 41 53.

Donations via the crowdfunding site are also very welcome.