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Background Patients with distant metastatic Medullary Thyroid Carcinoma (MTC) have an estimated 40% ten-year survival rate. Gain of function mutations in the REarranged during Transfection or RET gene in MTC can result in an aggressive phenotype resistant to traditional therapy. In this case report, we describe the treatment of an MTC patient with a unique RET kinase deletion mutation. Case presentation Since diagnosis, 21 years ago, this patient has had chronically elevated calcitonin levels (>40,000 pg/mL) that was unable to be controlled by conventual therapy and clinical trials. As result of uncontrolled MTC, metastatic disease was found in the spine, liver, and lungs. Circulating tumor DNA (ctDNA) analysis identified a RET 898-901Del mutation, reported as a variant of unknown significance. The treating physician identified that the deletion was in the activation loop of RET kinase and considered that the mutation was constitutively activating RET kinase. The patient was prescribed Pralsetinib, a small molecule inhibitor targeting the ATP binding site of RET. Pralsetinib treatment achieved a durable response and was able to significantly decrease serum calcitonin levels (<200 pg/mL) and tumor size. Conclusion This RET deletion mutation is a pathogenic mutation with comparable enzymatic activity to the more common RET M918T mutation. The case report highlights the versatility of structural biologic approaches to guide therapeutic decisions.
Background Hyperphenylalaninemia (HPA) combined with neurological signs due to impaired catecholamine, dopamine and serotonin synthesis. Symptoms may appears in first week of life but most seen in age of 4 months. Atypical PKU disease caused mainly by deficiency in 6-pyruvoyltetrahydropterin synthase (PTPS) involved in synthesis of BH4. Clinical symptoms may include poor sucking, impaired tone, ataxia, and seizures. The purpose of this study was to analyze the genotype-phenotype relation among BH4 deficient patients because of PTPS mutations in different state of Egypt. Methods Suspected PKU patients loaded with phenylalanine/Kuvan, and the level of phe and phe/tyrosine ratio determined using tandem mass spectrometry by dried blood spots. Blood samples of 13 unrelated Egyptian patients were collected for total RNA extraction, amplification of PTPS gene by PCR followed with sequencing by Sanger method and finally mutations were recorded for genetic analysis. Results The mean value of phe in 13 patients decreased after loaded of phenylalanine from 482.5μmol/L to 270.63 μmol/L as well as phe/tyrosine ratio was decreased from 13.4 to 6.36 after 24hour of treatment with Kuvan. Sanger sequencing of PTPS gene of those patient showed 21 SNPs and Indels mutations. The most repeated mutation is a novel 23 base pair homozygous deletion in 12/13; c.200C>T in four patients, a novel c.86A>T in two patients and three different mutations located once in three different patients (novel c.22C>T; novel c.273G>A and 405T>C) among patients. On amino acid predicted sequences 4 different types of mutations on protein level were presented, 1 deletion mutation in seven amino acid and 3 different missense mutations in addition to 2 silent mutations among 13 patients. Conclusion Patients were the first case of clinical diagnosis as hyperphenylalaninemia (HPA) undergoing genetic diagnosis for PTPS deficiency in Egypt. The sever HPA patients with severe nervous system damage mainly accompanied with deletion mutations and should pay more attention to the BH4 deficiency. While mild HPA is associated with base substitution mutations with mainly transition mutations (7/9; 78%). Next-generation sequencing technique can increase the mutation detection rate when the hereditary diseases are highly suspected in clinic.