Scientists have taken a big step towards treating a rare inherited disease by creating healthy cells from flakes of skin and strands of hair plucked from patients.

The study is the first to demonstrate that it is possible to repair genetic faults in human cells and make batches of healthy replacements that could potentially be used to treat a disease.

In a report in the journal Nature, researchers describe how they took skin and hair cells from six patients with a rare inherited blood disorder called Fanconi anaemia.

The disease is caused by a genetic defect that leads to bone marrow failure and a greater risk of cancers, such as leukaemia. People who are born with Fanconi anaemia are usually diagnosed in early childhood and rarely survive beyond 30 years old.

In a three-stage procedure, the researchers used gene therapy to fix the faulty DNA in the cells they had taken from patients. Next, they used a technique called cell reprogramming to convert these cells into healthy stem cells, which are unique in being able to grow into any kind of tissue in the body.

In the final stage of the process, the researchers grew the stem cells in petri dishes into early stage bone marrow cells, which in principle could be injected into patients to treat their condition.

"We haven't cured a human being, but we have cured a cell," said Juan-Carlos Izpisúa Belmonte, who led the study at the Salk Institute for Biological Studies in La Jolla, California. "[But] in theory we could transplant it into a human and cure the disease."

The feat will raise the hopes of stem cell scientists all over the world who are working on similar techniques to treat other inherited diseases. The technique is appealing because it uses a patient's own cells, which would not be rejected by the immune system.

The California team stopped short of injecting the healthy cells back into the six patients because they are not considered safe enough to be transplanted. The reason is that harmless viruses are used in the procedure, which could cause the cells to turn into tumours. Scientists are developing alternatives that do not rely on viruses.

"[This work shows] it is possible to reprogram skin cells from these patients into stem cells in which the genetic defect has been corrected. In future it may become possible to transfer the corrected stem cells back into the patient, but much work remains to be done before this can be transferred from the lab bench to the bedside." said Chris Matthews, professor of molecular genetics at King's College London.

Chris Mason, professor of regenerative medicine at University College London, added: "There is no doubt that this paper will be the first of many to offer hope for conditions where today there is no real therapy, let alone a cure."