Some patients with neuromuscular diseases may die more than a decade too soon because specialist services are too far away, a report says.
The diseases cause muscle weakness and wasting
It found people with muscular dystrophy in north east England - close to a centre of excellence - live an average of 30 years after diagnosis.
However, in the south west the average was just 18 years.
The Muscular Dystrophy Campaign report found two-thirds of areas in England do not offer the right kind of care.
The most common serious neuromuscular disease is Duchenne muscular dystrophy - one in every 3,500 boys has it.
Other neuromuscular illnesses include Charcot-Marie-Tooth disease, Becker muscular dystrophy and myasthenia gravis.
Neuromuscular diseases can lead to muscle weakness, wasting, and in some cases eventually to serious breathing problems.
In recent years, techniques such as offering breathing support machines at home have increased the average lifespan after diagnosis for Duchenne muscular dystrophy from 19 years to 30 years.
But the report says this advance simply is not available in a "systematic" way to patients in some parts of the country.
Muscular Dystrophy Campaign chief executive Philip Butcher said: "People with rare illnesses are living longer thanks to medical advances, and yet local NHS services are failing to meet this demand.
"It is essential that the Department of Health and the NHS recognise the specialist nature of the care needed by patients with neuromuscular diseases, and ensure that such services are available to all patients, regardless of where they live."
Report co-author and consultant neurologist Professor Mike Hanna said that proper care was "essential" to keep patients with neuromuscular diseases alive.
"It is simply unacceptable that life expectancy for conditions such as Duchenne muscular dystrophy can be halved, after diagnosis, depending on your postcode," he said.
The report says that there are only four centres of excellence in the country but that these are often dependent on just a few expert members of staff, and reliant on charitable funding to keep running.
The report includes a survey of primary care trusts in England conducted via Freedom of Information Act requests, which revealed that two out of three did not support a "muscle clinic" at local hospitals for patients.
One muscular dystrophy patient, Steve Ledbrook, described his local region, the south west, as a "desert" for treatment.
"Expecting disabled people and their families to travel long distances just to gain access to the clinical care they need is very disappointing and simply unfair," he said.
The report calls for the Department of Health to set guidelines for the care of patients with neuromuscular diseases.
A Department of Health spokesperson said the National Service Framework for Long-term Conditions, published in 2005, specifically covered the needs of patients with neuromuscular disease.
"It is the responsibility of local health services to provide services to meet the needs of people with Duchenne Muscular Dystrophy and other musculo-skeletal conditions."