TTP registry highlights challenges of rare diseases


By Tony James

19 Nov 2015

An Australian registry of patients with thrombotic thrombocytopenic purpura has highlighted the challenges for individual physicians and the health care system in responding to emergencies arising from very rare diseases.

The registry, maintained by the Monash University Department of Epidemiology and Preventive Medicine in partnership with the Australian Red Cross Blood Service, identified 72 clinical episodes of thrombotic thrombocytopenic purpura (TTP) in 57 patients between 2009 and 2014.

A report in the Internal Medicine Journal has emphasised the scope to improve care.

Lead author Dr Piers Blombery, consultant haematologist at the Peter MacCallum Cancer Centre in Melbourne, told the limbic that because TTP is a rare disease there is a significant risk of variations in practice.

“It’s a result of the infrequency with which individual physicians encounter TTP,” he says.

“The consequences of suboptimal management are magnified by its highly aggressive clinical course.

“Early recognition is critical. It begins in the laboratory with the identification of fragments on the blood film which should always be assumed to indicate a life-threatening disease process until proven otherwise.”

The registry data revealed considerable variation between the 37 contributing Australian and New Zealand centres in investigations, definitive management (including the choice and timing of immunosuppression and plasma exchange), and supportive care (for example, platelet transfusion).

“The registry is positioned to identify differences in management and deviation from accepted best practice, and assist expert clinicians in developing local guidelines, educating other practitioners and guiding future research,” Dr Blombery says.

“The exact incidence of TTP in Australia is unknown, but extrapolating from incidence data in the UK and USA this analysis likely represents only a fraction of the actual cases.

“Since this publication, however, the registry has put processes in place to increase the capture of patients.”

TTP is one of a group of thrombotic microangiopathies that lead to microvascular ischaemia and life-threatening end-organ dysfunction. They include haemolytic uraemic syndrome and conditions associated with malignancy, bone marrow transplantation and pregnancy.

“Clinically, TTP typically manifests as an abrupt-onset illness with constitutional symptoms, thrombocytopenia, microangiopathic haemolytic anaemia and neurological symptoms ranging from headache to coma,” Dr Blombery and his colleagues wrote.

“Whilst the clinical symptoms and laboratory abnormalities seen in TTP are not specific, the potential for rapid clinical deterioration and early mortality means that empiric treatment with therapeutic plasma exchange is often required before confirmation of diagnosis.”

Testing for ADAMTS13 activity is the gold standard diagnosis but it was performed in only nine of 57 patients, reflecting the limited availability of accredited testing facilities.

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