Non-balanced translocation between the short arms of chromosomes 8 and 6 associated with type 1 diabetes mellitus

SUMMARY: We describe a rare case of a girl with an initial diagnostic hypothesis of chromosome 8 trisomy based on clinical findings and karyotyping, which identified a structural change in the short arm of chromosome 8 (46,XX,add(8)(p23)). At the age of 7, she developed type 1 diabetes mellitus and started insulin therapy with multiple daily doses, and then she started to use a continuous insulin infusion system (pump) at 10 years of age. At the age of 12, she underwent a molecular study that identified an unbalanced translocation between the short arms of chromosomes 6 and 8 – 46,XX,add(8)(p23).ish der(8)t(6;8)(GS-196I5+;RP-11338B22−). LEARNING POINTS: Patients with an unbalanced translocation between the short arms of chromosomes 6 and 8 – 46,XX,add(8)(p23).ish der(8)t(6;8)(GS-196I5+;RP-11338B22-) may present syndromic features suggestive of chromosome 8 trisomy. Main characteristics are a prominent forehead, ocular and breast hypertelorism, ocular, external ear and palate abnormalities, a short neck, heart defects, and developmental delay. Patients with 46,XX,add(8)(p23).ish der(8)t(6;8)(GS-196I5+;RP-11338B22-) may present autoimmune type 1 diabetes mellitus. Karyotyping is an essential tool for the diagnosis of chromosomal changes, but it has some limitations. Multiplex ligation-dependent probe amplification, array-single nucleotide polymorphism and fluorescence in situ hybridization can help diagnose genetic syndromes in patients with atypical evolution.