THE SPECTRUM OF PRIMARY IMMUNODEFICIENCY DISORDERS IN AUSTRALIA

Background: Primary immunodeficiency disorders (PIDs) are uncommon con ditions that require specialized immunologic services for diagnosis an d management. It is difficult to estimate the prevalence of these diso rders from routinely collected health statistics. Objective: We attemp ted to describe the prevalence of PID in Australia and the requirement s for specific therapies, such as intravenous immunoglobulin, ascertai ned from a national register of PID. Methods: A national longitudinal cross-sectional survey of patients with PID under the care of clinical immunologists was established by the Australasian Society of Allergy and Clinical Immunology in 1990. Details of diagnosis and therapy were provided for patients with major PIDs including symptomatic IgA, IgG subclass, and complement deficiencies. Subjects with asymptomatic IgA deficiency were not included. The clinical features of the first 500 c ases enrolled in the register were analyzed. Results: The most frequen t type of PID was predominant antibody deficiency (71%). Common variab le immunodeficiency, usually first seen as an antibody deficiency, was the single mast common disorder with an estimated prevalence of 0.77/ 100,000 in the general population. Other types of PID were infrequent, and of these, severe combined immunodeficiency accounted for 5.2% of cases. The estimated prevalence of all forms of chronic granulomatous disease was 0.08/ 100,000. The national prevalence of all PID cases as certained from the register was 2.1/100,000, with variation between th e larger states ranging from 1.18 to 4.57/100,000. Half (247) of the p atients were receiving intravenous immunoglobulin therapy with a media n duration of care of 5 to 9 years for the different antibody deficien cies. There was also variation in the patterns of intravenous immunogl obulin use across the country. No new forms of PID were encountered. C onclusion: This study highlights the requirement for the continuing pr ovision of immunoglobulin as replacement therapy for these patients. I n addition, the register documents a cohort of patients with PID whose long-term response to current therapy can be evaluated prospectively.