RESUMO
Maturity onset diabetes of the young (MODY) is characterized by noninsulin-dependent diabetes diagnosed at a young age (<25 years) with an autosomal dominant inheritence. Rare mutations in the hepatocyte nuclear factor-1-beta (HNF1B) gene produce a syndrome that resemble MODY and about half of patients diagnosed with MODY5 (HNF1B mutation) have a a whole gene deletion, called as 17q12 deletion syndrome, is a rare chromosomal anomaly and is typified by deletion of the more than 15 genes including HNF1B resulting in kidney abnormalities and renal cysts and diabetes syndrome and neurodevelepmental or neuropsychiatric disorders. A 12-year-old girl was referred to our clinic, after high blood sugar was detected in the hospital where she suffered with the complaints of poliuria and polydipsia for the last 1 month. Her serum magnessium level was low (1.5 mg/dl) (normal value 1.6-2.6) and HbA1c level was 14% (normal value 3.6-5.8) and c-peptide level was 1.54 ng/ml (normal value 0.8-4). MODY5 was suspected and followed NGS gene panel (ABCC8, BLK, CEL, GCK, HNF1A, HNF1B, HNF4A, INS, KCNJ11, KLF11, NEURODD1, PAX4, PDX1, RFX6, ZFP57, GLIS3, FOXP3, NEUROG3, G6PC2) analysis revealed that there was no any mutation. On follow-up period, her serum magnessium level was low (1.2 mg/dl) and her urinary magnessium excretion was high at 172.5 mg/day. HNF1B gene mutation was considered in the patient with chronic hypomagnesemia with increased basal C peptide level. Abdominal CT and MR imagings revealed that there was a 43 mm diameter cystic lesion in the head of the pancreas, and agenesis of the pancreatic neck, trunk and tail as well. Because of there is no mutation in HBF1B gene in NGS panel, microarray analysis was performed, heterozygous deletion at 17q12 including HNF1B was detected. The HNF1B mutation is difficult to diagnose and has a large phenotypic variation . In case of clinical suspicion,further genetic examination (MLPA, array CGH) may be required since deletions and duplications can not be detected even if mutations in the HNF1B gene are not detected with NGS.
RESUMO
Introduction: Germline pathogenic variations of the genes encoding the components of the Ras-MAPK pathway are found to be responsible for RASopathies, a clinically and genetically heterogeneous group of diseases. In this study, we aimed to present the results of patients genetically investigated for RASopathy-related mutations in our Genetic Diagnosis Center. Methods: The results of 51 unrelated probands with RASopathy and 4 affected relatives (31 male, 24 female; mean age: 9.327 ± 8.214) were included in this study. Mutation screening was performed on DNA samples from peripheral blood of the patients either by Sanger sequencing of PTPN11 hotspot regions (10/51 probands), or by a targeted amplicon next-generation sequencing panel (41/51 probands) covering the exonic regions of BRAF, CBL, HRAS, KRAS, LZTR1, MAP2K1, MAP2K2, NF1, NRAS, PTPN11, RAF1, RASA2, RIT1, SHOC2, SOS1, SOS2, SPRED1, and KAT6B genes. Results: Pathogenic/likely pathogenic variations found in 22 out of 51 probands (43.13%) and their 4 affected family members were located in PTPN11, BRAF, KRAS, NF1, RAF1, SOS1, and SHOC2 genes. The c.148A>C (p.Thr50Pro) variation in the KRAS gene was a novel variant detected in a sibling in our patient cohort. We found supportive evidence for the pathogenicity of the NF1 gene c.5606G>T (p.Gly1869Val) variation which we defined in an affected boy who inherited the mutation from his affected father. Conclusion: Although PTPN11 is the most frequently mutated gene in our patient cohort, as in most previous reports, different mutation distribution among the other genes studied motivates the use of a next-generation sequencing gene panel including the possible responsible genes.
