Diagnostic value of serum immunoglobulinaemia D level in patients with a clinical suspicion of hyper IgD syndrome.

Objective: The hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS) was originally defined by the presence of a high serum level of immunoglobulin D associated with recurrent fever. Since the discovery of the mevalonate kinase gene (MVK) gene encoding the mevalonate kinase enzyme, most patients with a clinical diagnostic of HIDS are now found to have a mevalonate kinase deficiency based on metabolic and genetic data. We aimed to asses the value of a high IgD serum level for the diagnosis of HIDS in a cohort of patients with a phenotype of recurrent fever, and to characterize patients with a high IgD serum level without mevalonate kinase mutation.

Methods: Main clinical and biological data of 50 patients who presented with clinical signs compatible with HIDS have been prospectively registered on a standard form. Clinical data have been analysed according the IgD serum level and the presence of MVK mutation.

Results: The metabolic and genetic data establishing the diagnosis of HIDS correlated in all cases. In this series of 50 patients, the sensitivity of a high IgD value for the diagnosis of HIDS is 0.79. In five patients with MVK mutation, IgD levels were found to be in the normal range. Likelihood ratios indicate that IgD measurement is not relevant for the diagnostic of HIDS. Most patients with a high serum IgD level and no MVK mutation have no definite diagnosis.

Conclusion: The clinical relevance of the IgD measurement for the diagnosis of MKD in our population appears as poor, as reflected by likelihood ratios which are both close to 1.