Outpatient rheumatology appointments for around 850 people in the west have been postponed until later this year because of staff shortages.
The Health Service Executive says a number of clinics scheduled to take place at Merlin Park Hospital in Galway have been cancelled during the summer months.
People with inflammatory conditions - such as rheumatoid arthritis - are routinely reviewed at outpatient clinics.
Intervention is seen as central to easing symptoms and aiding pain management.
The HSE's Saolta Hospital Group has confirmed that those with outpatient appointments for Galway in July and August are now being informed that their visits will be rescheduled.
A combination of leave and vacant posts has contributed to appointments being postponed.
The vast majority of those affected live in Galway, Mayo and Roscommon.
Some patients have already been offered new appointments, but not until late December.
This delay will further compound waiting lists for those seeking to attend the two outpatient clinics in the Saolta group.
The Dáil today heard that a number of consultants will take up positions in Galway over the coming months.
Speaking during Leaders' Questions, Labour Minister Alex White said a locum consultant will take up a post in September this year, "an extra consultant" in October, and one for rheumatology in July.
He said patients will receive a new appointment as soon as possible.
Mr White was responding to Fianna Fáil's Dara Calleary, who asked if it was acceptable that a consultant who had gone on maternity leave would not be replaced until December.
Mr Calleary said there was a failure in planning.
At the moment almost 1,500 people are waiting to see a consultant in Galway, while over 1,000 are seeking appointments at Our Lady's Hospital in Manorhamilton, Co Leitrim.
Clinics there will continue as normal during the summer months.
The HSE says it is in the process of recruiting additional staff, but no new consultants will be available before September.
During the summer months, emergency patients will continue to be seen on a case-by-case basis.