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Florian W Kiefer, Yvonne Winhofer, Donato Iacovazzo, Márta Korbonits, Stefan Wolfsberger, Engelbert Knosp, Franz Trautinger, Romana Höftberger, Michael Krebs, Anton Luger and Alois Gessl

Context

Carney complex (CNC) is an autosomal dominant condition caused, in most cases, by an inactivating mutation of the PRKAR1A gene, which encodes for the type 1 alpha regulatory subunit of protein kinase A. CNC is characterized by the occurrence of endocrine overactivity, myxomas and typical skin manifestations. Cushing syndrome due to primary pigmented nodular adrenocortical disease (PPNAD) is the most frequent endocrine disease observed in CNC.

Case description

Here, we describe the first case of a patient with CNC and adrenocorticotropic hormone (ACTH)-dependent Cushing disease due to a pituitary corticotroph adenoma. Loss-of-heterozygosity analysis of the pituitary tumour revealed loss of the wild-type copy of PRKAR1A, suggesting a role of this gene in the pituitary adenoma development.

Conclusion

PRKAR1A loss-of-function mutations can rarely lead to ACTH-secreting pituitary adenomas in CNC patients. Pituitary-dependent disease should be considered in the differential diagnosis of Cushing syndrome in CNC patients.

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Donato Iacovazzo, Eivind Carlsen, Francesca Lugli, Sabrina Chiloiro, Serena Piacentini, Antonio Bianchi, Antonella Giampietro, Marilda Mormando, Andrew J Clear, Francesco Doglietto, Carmelo Anile, Giulio Maira, Libero Lauriola, Guido Rindi, Federico Roncaroli, Alfredo Pontecorvi, Márta Korbonits and Laura De Marinis

Aim

To gather data regarding factors predicting responsiveness to pasireotide in acromegaly.

Patients and methods

SSTR2a, SSTR3, SSTR5, AIP, Ki-67 and the adenoma subtype were evaluated in somatotroph adenomas from 39 patients treated post-operatively with somatostatin analogues (SSAs). A standardized SSTR scoring system was applied (scores 0–3). All patients received first-generation SSAs, and 11 resistant patients were subsequently treated with pasireotide LAR.

Results

None of the patients with negative or cytoplasmic-only SSTR2a expression (scores 0–1) were responsive to first-generation SSAs, as opposed to 20% (score 2) and 50% of patients with a score of 3 (P=0.04). None of the patients with an SSTR5 score of 0–1 were responsive to pasireotide, as opposed to 5/7 cases with a score of 2 or 3 (P=0.02). SSTR3 expression did not influence first-generation SSAs or pasireotide responsiveness. Tumours with low AIP were resistant to first-generation SSAs (100 vs 60%; P=0.02), while they had similar responsiveness to pasireotide compared to tumours with conserved AIP expression (50 vs 40%; P=0.74). Tumours with low AIP displayed reduced SSTR2 (SSTR2a scores 0–1 44.4 vs 6.7%; P=0.006) while no difference was seen in SSTR5 (SSTR5 scores 0–1 33.3 vs 23.3%; P=0.55). Sparsely granulated adenomas responded better to pasireotide compared to densely granulated ones (80 vs 16.7%; P=0.04).

Conclusion

The expression of SSTR5 might predict responsiveness to pasireotide in acromegaly. AIP deficient and sparsely granulated adenomas may benefit from pasireotide treatment. These results need to be confirmed in larger series of pasireotide-treated patients.

Open access

Roberto Salvatori, Serban Radian, Yoan Diekmann, Donato Iacovazzo, Alessia David, Plamena Gabrovska, Giorgia Grassi, Anna-Marie Bussell, Karen Stals, Astrid Weber, Richard Quinton, Elizabeth C Crowne, Valentina Corazzini, Lou Metherell, Tara Kearney, Daniel Du Plessis, Ajay Kumar Sinha, Atik Baborie, Anne-Lise Lecoq, Philippe Chanson, Olaf Ansorge, Sian Ellard, Peter J Trainer, David Balding, Mark G Thomas and Márta Korbonits

Objective

Mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are associated with pituitary adenoma, acromegaly and gigantism. Identical alleles in unrelated pedigrees could be inherited from a common ancestor or result from recurrent mutation events.

Design and methods

Observational, inferential and experimental study, including: AIP mutation testing; reconstruction of 14 AIP-region (8.3 Mbp) haplotypes; coalescent-based approximate Bayesian estimation of the time to most recent common ancestor (tMRCA) of the derived allele; forward population simulations to estimate current number of allele carriers; proposal of mutation mechanism; protein structure predictions; co-immunoprecipitation and cycloheximide chase experiments.

Results

Nine European-origin, unrelated c.805_825dup-positive pedigrees (four familial, five sporadic from the UK, USA and France) included 16 affected (nine gigantism/four acromegaly/two non-functioning pituitary adenoma patients and one prospectively diagnosed acromegaly patient) and nine unaffected carriers. All pedigrees shared a 2.79 Mbp haploblock around AIP with additional haploblocks privately shared between subsets of the pedigrees, indicating the existence of an evolutionarily recent common ancestor, the ‘English founder’, with an estimated median tMRCA of 47 generations (corresponding to 1175 years) with a confidence interval (9–113 generations, equivalent to 225–2825 years). The mutation occurred in a small tandem repeat region predisposed to slipped strand mispairing. The resulting seven amino-acid duplication disrupts interaction with HSP90 and leads to a marked reduction in protein stability.

Conclusions

The c.805_825dup allele, originating from a common ancestor, associates with a severe clinical phenotype and a high frequency of gigantism. The mutation is likely to be the result of slipped strand mispairing and affects protein–protein interactions and AIP protein stability.