Nuria Valdés, Elena Navarro, Jordi Mesa, Anna Casterás, Victoria Alcázar, Cristina Lamas, Javier Tébar, Luis Castaño, Sonia Gaztambide and Lluís Forga
Specific germline mutations in the RET proto-oncogene are correlated with clinical features in multiple endocrine neoplasia type 2A (MEN2A); however, data are scarce regarding differences in clinical profiles dependent on the type of nucleotide and amino acid substitution at the same codon. We aimed to analyse differences in clinical risk profiles and outcomes among different amino acids encoded by codon 634.
The study was retrospective and multicentric.
We collected data included in the Spanish Online National Database from patients with MEN2A carrying a RET proto-oncogene mutation on codon 634. The mean follow-up time was 7.6±6.9 years (1–32).
Patients (n=173) from 49 unrelated families were C634Y carriers, and 26 patients from eight different families had C634R mutation. We found higher penetrance of medullary thyroid carcinoma, phaeochromocytoma and hyperparathyroidism (P<0.001, P=0.007 and P<0.001 respectively) in C634R carriers than in C634Y carriers. The Kaplan–Meier estimate of cumulative lymph node and distant metastases rates showed that these events occurred earlier in patients harbouring the C634R mutation (P<0.001). A multivariate adjusted Cox regression analysis indicated that the C634R mutation was an independent factor for persistent/recurrent disease (hazard ratio, 3.17; 95% CI: 1.66–6.03; P<0.001).
Our results suggest that there could be clinical differences caused by different amino acid substitutions at codon 634; specifically, the C634R mutation was associated with a more aggressive MEN2A phenotype than the C634Y mutation.
Alejandro García-Castaño, Leire Madariaga, Gustavo Pérez de Nanclares, Gema Ariceta, Sonia Gaztambide, Luis Castaño and Spanish Endocrinology Group and Renal Tube Group
Molecular diagnosis is a useful diagnostic tool in calcium metabolism disorders. The calcium-sensing receptor (CaSR) is known to play a central role in the regulation of extracellular calcium homeostasis. We performed clinical, biochemical and genetic characterization of sequence anomalies in this receptor in a cohort of 130 individuals from 82 families with suspected alterations in the CASR gene, one of the largest series described.
The CASR gene was screened for mutations by polymerase chain reaction followed by direct Sanger sequencing.
Presumed CaSR-inactivating mutations were found in 65 patients from 26 families. These patients had hypercalcemia (median: 11.3 mg/dL) but normal or abnormally high parathyroid hormone (PTH) levels (median: 52 pg/mL). On the other hand, presumed CaSR-activating mutations were detected in 17 patients from eight families. These patients had a median serum calcium level of 7.4 mg/dL and hypoparathyroidism (median: PTH 13 pg/mL). Further, common polymorphisms previously associated with high blood ionized calcium levels were found in 27 patients (median calcium: 10.6 mg/dL; median PTH: 65 pg/mL) with no other alterations in CASR. Overall, we found 30 different mutations, of which, 14 have not been previously reported (p.Ala26Ser, p.Cys60Arg, p.Lys119Ile, p.Leu123Met, p.Glu133Val, p.Gly222Glu, p.Phe351Ile, p.Cys542Tyr, p.Cys546Gly, p.Cys677Tyr, p.Ile816Val, p.Ala887Asp, p.Glu934*, p.Pro935_Gln945dup).
Patients with CASR mutations may not fit the classic clinical pictures of hypercalcemia with hypocalciuria or hypocalcemia with hypercalciuria. Molecular studies are important for confirming the diagnosis and distinguishing it from other entities. Our genetic analysis confirmed CaSR disorders in 82 patients in the study cohort.