A Welsh health board has become the first NHS body to be fined for breaching the Data Protection Act after it released sensitive data about a patient to the wrong person.
Aneurin Bevan Health Board (ABHB) will have to pay a £70,000 penalty.
A doctor misspelt a name and did not give enough detail about a patient to his secretary, meaning a report was sent to someone with a similar name.
The board has apologised to the patient concerned.
The Information Commissioner's Office (ICO) said the report contained explicit details relating to the patient's health and represented a serious breach of the Data Protection Act.
The error occurred when the patient's consultant emailed a letter to a secretary but did not provide enough information for the secretary to be able to identify the correct person.
The mistake was compounded by the doctor misspelling the patient's name at one point, which resulted in the report being sent to a former patient with a very similar name in March last year.
An investigation by the ICO found neither member of staff had received training in data protection and there were inadequate checks in place within the board to ensure personal information was only sent to the correct recipient.
These poor practices were also used by other clinical and secretarial staff across the organisation.
Stephen Eckersley, the ICO's head of enforcement said: "The health service holds some of the most sensitive information available.
"The damage and distress caused by the loss of a patient's medical record is obvious, therefore it is vital that organisations across this sector make sure their data protection practices are adequate.
"Aneurin Bevan Health Board failed to have suitable checks in place to keep the sensitive information they handled secure. This case could have been extremely distressing to the individual and their family and may have been prevented if the information had been checked prior to it being sent.
"We are pleased that the health board has now committed to taking action to address the problems highlighted by our investigation; however organisations across the health service must stand up and take notice of this decision if they want to avoid future enforcement action from the ICO."
ABHB is introducing some measures following the incident including ensuring all staff are trained on the storage and use of data policies, regular monitoring of compliance with data protection and IT policies, and new checking processes to confirm a patient's identity before personal information is sent out.
The board has signed an undertaking to address the ICO's concerns.
A spokesman for ABHB said it had approached the patient before contacting the information commission to apologise and make the person aware of events.
The board said it was disappointed by the penalty as it took protecting patient information seriously.
"We have 14,000 staff and have hundreds of thousands of contacts with patients each year, with systems in place to discharge these patient contacts confidentially," said the spokesman.
"The health board has always sought to be compliant with the commissioner's requirements for public service organisations in this critical area.
"This was a genuine and unintended individual error, which was self-reported by the organisation to the information commissioner, because of the importance the health board places on information governance and in line with the commissioner's own guidance."