Background: Periodic fever can have one of multiple causes. Among the hereditary periodic fever syndromes, hyper-IgD syndrome (HIDS) is a possible diagnosis, although, until now, no cases had been described in Portugal.
Case-report: We report a 25-year-old woman, with periodic fever since she was 8 months old. She had high serum IgD levels, and a molecular study of the mevalonate kinase gene was performed. A compound heterozygote was found for two mutations: V377I and T237S. This last mutation had not been observed before.
Discussion: We analyse the clinical features that made us think on HIDS as a possible diagnosis, and we highlight the features that are important for the differential diagnosis between HIDS and other periodic fevers.
Conclusions: HIDS is a possible diagnosis for patients with periodic fever, even in Portugal.