Elevated immunoglobulin D levels in children with PFAPA syndrome.

BACKGROUND: The periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA) syndrome appears to be more common than generally appreciated and should be differentiated from hereditary periodic fever syndromes, particularly from mevalonate kinase deficiency (MKD).

PATIENTS AND METHODS: 14 unrelated patients (7 males, 7 females) met clinical criteria for both the PFAPA syndrome and MKD. Immunoglobulin D (IgD) levels, mevalonic aciduria and mevalonate kinase (MVK) genotype was determined in all patients.

RESULTS: Children experienced their first febrile episode at the age of 24.5±5.9 months (mean±SD), the clinical diagnosis of PFAPA syndrome was established with delay at 42.7±11.7 months. The duration of febrile episodes was 3.4±0.2 days, the asymptomatic interval between them lasted 5.4±0.9 weeks. Accompanying symptoms included pharyngitis (92.8%), cervical lymphadenitis (85.7%), aphthous stomatitis (21.4%), arthralgia (14.3%) and skin erythema (35.7%). Neither mevalonic aciduria nor MVK gene mutations were found in any of the subjects, however, unexpectedly, increased plasma IgD (322.2±29.2 U/l) levels were detected in all patients.

CONCLUSION: Raised IgD levels may represent a non-specific epiphenomenon, which frequently accompanies PFAPA syndrome as well as MKD. Because of the overlapping clinical and laboratory features, genetic testing of the MVK gene is indicated to differentiate these two conditions, if clinical criteria for both are fulfilled.