Endocrine Abstracts

Hepatocyte nuclear factor 1B (HNF1B) defects (mutations or deletion) are associated with amultisystem disorder, including urinary tract abnormalities and diabetes (MODY 5, maturity-onset diabetes of the young type 5). We present the case of a patient with congenital anomalies of the kidney and urinary tract in the context of 17q12 deletion syndrome who several years later, presented with MODY 5. A 20-year-old male presented at the outpatient Endocrine Clinic with new-onset diabetes mellitus. Laboratory findings revealed a HbA1c of 7.9%, with no evidence of ketoacidosis, detectable C- peptide levels (2.3 ng/ml) and negative antibodies to glutamic acid decarboxylase (GAD), tyrosine phospahtase (IA2) and insulin (IAA). He had a history of right ureterovesical junction obstruction repaired at the age of 2 and persistent hypomagnesemia, hypermagnesuria and hypocalciuria were found at the age of 15. A deletion of 1.4 Mb at chromosomal band 17q12 was then detected by array-comparative genomic hybridization, encompassing two OMIM genes, the Acetyl-CoaCarboxylase-Alpha (ACACA, OMIM#200350) and Hepatocyte Nuclear Factor-1-B (HNF-1B, OMIM#1890907). Elevated liver enzymes had been noted since the age of 17, and hypoplasia of the pancreas had been detected on an MRI scan. In addition, the patient exhibited learning difficulties, and mild mental retardation had been documented at the age of 16 (Wechsler Intelligence Scale III-R Full scale IQ score: 58). Based on the phenotypic features and results of the genetic analysis, a diagnosis of 17q12 deletion syndrome was made. The 17q12 deletion syndrome is caused by deletion of a 1.4 Mb region of 17q12 which encompasses genes like HNF-1B, ACACA and LHX1. Clinical features include diabetes mellitus of the MODY 5 type, functional and structural kidney and urinary tract disorders, cholestatic hepatopathy, structural pancreas malformations, intellectual/learning disabilities, neuropsychiatric disorders and facial dysmorphia. Recent evidence suggests that MODY 5 is a common feature in patients with 17q12 deletion syndrome whilston the other hand, whole gene HNF1B deletions are observed in up to 50% of MODY 5 cases. Notably, as recently reported by Laffargue et al., complete deletion of the HNF1B gene and 17q12 microdeletion syndrome may be considered as the same genetic disorder (5). Clinical features suggestive of the 17q12 deletion syndrome should prompt clinicians to request chromosomal microarray analysis in patients with suspected MODY 5.