Effect of inflammatory attacks in the classical type hyper-IgD syndrome on immunoglobulin D, cholesterol and parameters of the acute phase response.

Background. Classical type hyper-immunoglobulin D (IgD) syndrome (HIDS) is an hereditary auto-inflammatory disorder, characterized by recurrent episodes of fever, lymphadenopathy, abdominal distress and a high serum concentration of IgD. It is caused by mevalonate kinase deficiency. Objective. To further characterize the acute phase response during fever attacks in HIDS in order to improve diagnosis. Subjects. Twenty-two mevalonate kinase-deficient HIDS patients. Methods. Blood samples were drawn during and in between febrile attacks, and concentrations ofC-reactive protein (CRP), ferritin, procalcitonin, pentraxin 3, IgD and cholesterol in several lipoprotein fractions were determined. Results. The marked acute phase response at the time of a fever attack in classical type HIDS is reflected by a rise in CRP accompanied by a moderate but statistically significant rise in procalcitonin and pentraxin 3. In only two of 22 patients, procalcitonin concentration rose above 2 ng mL(-1) during fever attack, compatible with the noninfectious nature of these attacks. Ferritin does not reach the high concentrations found in adult-onset Still's disease. Despite the defect in mevalonate kinase, a component of cholesterol metabolism, serum cholesterol did not change during attacks. IgD concentration is elevated regardless of disease activity, although there is appreciable variation during life. Its role in HIDS remains unclear. Conclusion. The combination of high CRP concentration plus procalcitonin concentration <2 ng mL(-1) in a symptomatic HIDS patient might indicate a febrile attack without (bacterial) infection; this observation warrants further investigation for its usefulness as a marker in clinical practice.