Constitutional trisomy 8 and Behçet syndrome.

The characteristic clinical features of constitutional trisomy 8 include varying degrees of developmental delay, joint contractures and deep palmar and plantar creases. There is in established literature, which describes features of Behcet syndrome occurring in phenotypically normal individuals with myelodysplastic syndromes and trisomy 8 in their bone marrow. In this article, we describe four patients with constitutional trisomy 8, all with varying clinical phenotypes, who developed features of Behcet, in particular but not exclusively mucocutaneous ulceration. In addition, we examined gene copy numbers of the variable-number neutrophil defensin genes DEFA1A3 in one of the cases (case 1) and her parents, together with 14 cases of Behcet syndrome in comparison with 121 normal controls. The gene copy number was highest in case 1 (copy number 14) and was also increased in her parents (both copy number 9). However the mean copy number for DEFA1A3 among the 14 Behcet syndrome patients was actually lower (5.1) than among the controls (mean of 6.8 copies). Thus, we conclude that patients with constitutional trisomy 8 and those with trisomy 8 confined to the bone marrow are both at increased risk of developing features of Behcet syndrome. The mechanism may relate to increased chromosome 8 gene dosage with further analysis of candidate genes on chromosome 8 required. (c) 2009 Wiley-Liss, Inc.