In 1984, Van der Meer first reported six patients with a long history of recurrent attacks of fever of unknown cause and a constantly elevated polyclonal IgD (> 100 U/mL); he suggested the acronym of "hyper-IgD syndrome" (HIDS). A recent literature review identified 60 cases (59 from Europe and 1 from Japan). The mean age was 27 years (range: 3-69 years). The family studies have shown a positive family history for periodic fever (40% out of the patients) but not for hyper-IgD. The median age at onset was 0.5 years (range from the first weeks of life to 53 years). The length of the febrile attacks, though variable, lasted from 3 to 7 days. The frequency of the attacks varied among the individual patients, but in general it was once a month or bimonthly. The fever was sustained in all 60 patients (from 38 degrees C to 41 degrees C), with a rapid rose, a plateau and a slow decline to normal values over 5 days. The associated clinical findings involve abdominal symptoms (pain, vomiting, diarrhea), recurrent peritonitis, lymphadenopathy, splenomegaly, articular manifestations (non-destructive recurrent arthritis) and skin lesions (vasculitis). The prognosis is benign. The aetiopathogenesis of HIDS is unknown. The role of IgD in the pathogenesis remains to be elucidated. The therapy is only supportive.