The service gap is a result of the current bureaucratic arrangement between the Department of Health and the Hospital Authority.

In the public hospital system, only the two teaching hospitals - Queen Mary in Pok Fu Lam and Prince of Wales in Sha Tin - have a specialist-led dermatology team.

Other public hospitals rely on the dermatology service provided by the Health Department's social hygiene clinics. One of the clinics' key roles is to treat sexually transmitted diseases, especially among prostitutes.

The department sends dermatologists to six major public hospitals on request to care for inpatients. But it does not cover second-line hospitals, which must transport patients to clinics for outpatient treatment.

'The arrangement asking inpatients to seek outpatient treatment is absurd,' Siu said. 'Some patients are unstable; that's exactly why they are in hospital.'

Siu, who formerly worked at Wan Chai's Ruttonjee Hospital, said he knew of at least two elderly patients who had died from skin disease complications in the past two years.

He said he decided to speak up after seeing patients suffering.

On one occasion, a Department of Health dermatologist he had asked for urgent help told him that he could not break the rules. 'He could give me advice on the phone but his department would not allow him to come to see the patient,' Siu said.

'Skin disease is a blind spot in public hospital services. The authority should have its own specialists to care for public patients. Sometimes patients and their families ask why proper treatment cannot be given. We just tell them we have no skin doctors.'

Siu, who now works in the intensive care unit at Yan Chai Hospital, Tsuen Wan, recalled a case about three months ago of a middle-aged patient who developed serious infections from a skin disease. As Yan Chai Hospital is not covered by the Department of Health's 'outreach' dermatology services, Siu said he contacted Queen Mary Hospital's dermatology team to take the patient as a 'burns case'.

Dr Cheung Wai-lun, the Hospital Authority's director of cluster services, said most skin diseases could be handled at outpatient clinics.

'We admit there is a service gap because not all public hospitals are covered by this service,' he said. 'The authority has no expertise in skin services. We have to rely on the Department of Health ... It is not a priority among many other services, but of course we can explore with the department how to enhance services.'

The Department of Health social hygiene clinics have 32 doctors, including 13 specialists. The Hospital Authority has only two specialists in dermatology, one at Prince of Wales and the other at Queen Mary.

The department provides inpatient skin consultations at six hospitals: Queen Elizabeth (Yau Ma Tei), Princess Margaret (Lai Chi Kok), Prince of Wales, Tuen Mun, Pamela Youde Nethersole Eastern (Chai Wan) and Kwong Wah (Yau Ma Tei). Frequency of service varies from every working day to weekly.

A department spokesman said no urgent consultation was available for inpatients because such cases should be handled by doctors at hospitals. 'Only cases with diagnostic problems, refining management and chronic follow-up planning will be referred to dermatologists for expert opinion. Hence, there is no pledge about waiting times for inpatient consultations in most hospitals.'

The department said most patients with severe skin conditions were seen within a week. 'For those that are not stable enough for transfer, they should first be managed to a stable condition before referral,' the spokesman said.

Patients Rights Association spokesman Tim Pang Hung-cheong said all inpatient dermatology services should be staffed by the Hospital Authority. 'The current arrangement is too fragmented and risks patients' lives,' he said.

Association of Specialists in Dermatology president Dr Henry Chan Hin-lee said some skin diseases had a mortality rate of 16 per cent and should be handled by specialists.

'For some diseases, patients have blisters all over the body and some have very poor immunity,' he said. 'These diseases are fatal and should be managed by qualified dermatologists. But with the limited resources available now, the authority has been asking doctors with insufficient training to treat those patients.'

Chan said an example was United Christian Hospital in Kwun Tong, where a paediatrician was treating adult skin diseases.

In response to the association's criticism, United Christian Hospital said the paediatrician had 10 years' experience treating skin problems and had been trained in general dermatology in Britain.