The spectrum of primary immunodeficiency disorders in Australia

Background: Primary immunodeficiency disorders (PIDs) are uncommon conditions that require specialized immunologic services for diagnosis and management. It is difficult to estimate the prevalence of these disorders from routinely collected health statistics. Objective: We attempted to describe the prevalence of PID in Australia and the requirements for specific therapies, such as intravenous immunoglobulin, ascertained 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 cases enrolled in the register were analyzed. Results: The most frequent type of PID was predominant antibody deficiency (71%). Common variable 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 ascertained from the register was 2.1/100,000, with variation between the larger states ranging from 1.18 to 4.57/100,000. Half (247) of the patients were receiving intravenous immunoglobulin therapy with a median duration of care of 5 to 9 years for the different antibody deficiencies. There was also variation in the patterns of intravenous immunoglobulin use across the country. No new forms of PID were encountered. Conclusion: This study highlights the requirement for the continuing provision of immunoglobulin as replacement therapy for these patients. In addition, the register documents a cohort of patients with PID whose long-term response to current therapy can be evaluated prospectively.