Germline or somatic GPR101 duplication leads to X-linked acrogigantism: a clinico-pathological and genetic study.

Non-syndromic pituitary gigantism can result from AIP mutations or the recently identified Xq26.3 microduplication causing X-linked acrogigantism (XLAG). Within Xq26.3, GPR101 is believed to be the causative gene, and the c.924G > C (p.E308D) variant in this orphan G protein-coupled receptor has been suggested to play a role in the pathogenesis of acromegaly.We studied 153 patients (58 females and 95 males) with pituitary gigantism. AIP mutation-negative cases were screened for GPR101 duplication through copy number variation droplet digital PCR and high-density aCGH. The genetic, clinical and histopathological features of XLAG patients were studied in detail. 395 peripheral blood and 193 pituitary tumor DNA samples from acromegaly patients were tested for GPR101 variants.We identified 12 patients (10 females and 2 males; 7.8 %) with XLAG. In one subject, the duplicated region only contained GPR101, but not the other three genes in found to be duplicated in the previously reported patients, defining a new smallest region of overlap of duplications. While females presented with germline mutations, the two male patients harbored the mutation in a mosaic state. Nine patients had pituitary adenomas, while three had hyperplasia. The comparison of the features of XLAG, AIP-positive and GPR101&AIP-negative patients revealed significant differences in sex distribution, age at onset, height, prolactin co-secretion and histological features. The pathological features of XLAG-related adenomas were remarkably similar. These tumors had a sinusoidal and lobular architecture. Sparsely and densely granulated somatotrophs were admixed with lactotrophs; follicle-like structures and calcifications were commonly observed. Patients with sporadic of familial acromegaly did not have an increased prevalence of the c.924G > C (p.E308D) GPR101 variant compared to public databases.In conclusion, XLAG can result from germline or somatic duplication of GPR101. Duplication of GPR101 alone is sufficient for the development of XLAG, implicating it as the causative gene within the Xq26.3 region. The pathological features of XLAG-associated pituitary adenomas are typical and, together with the clinical phenotype, should prompt genetic testing.

AIP mutations in young patients with acromegaly and the Tampico Giant: the Mexican experience.

Although aryl hydrocarbon receptor-interacting protein (AIP) mutations are rare in sporadic acromegaly, their prevalence among young patients is nonnegligible. The objectives of this study were to evaluate the frequency of AIP mutations in a cohort of Mexican patients with acromegaly with disease onset before the age of 30 and to search for molecular abnormalities in the AIP gene in teeth obtained from the "Tampico Giant". Peripheral blood DNA from 71 patients with acromegaly (51 females) with disease onset <30 years was analysed (median age of disease onset of 23 years) and correlated with clinical, biochemical and imaging characteristics. Sequencing was also carried out in DNA extracted from teeth of the Tampico Giant. Five patients (7 %) harboured heterozygous, germline mutations of the AIP gene. In two of them (a 9-year-old girl with gigantism and a young man with symptoms of GH excess since age 14) the c.910C>T (p.Arg304Ter), well-known truncating mutation was identified; in one of these two cases and her identical twin sister, the mutation proved to be a de novo event, since neither of their parents were found to be carriers. In the remaining three patients, new mutations were identified: a frameshift mutation (c.976_977insC, p.Gly326AfsTer), an in-frame deletion (c.872_877del, p.Val291_Leu292del) and a nonsense mutation (c.868A > T, p.Lys290Ter), which are predicted to be pathogenic based on in silico analysis. Patients with AIP mutations tended to have an earlier onset of acromegaly and harboured larger and more invasive tumours. A previously described genetic variant of unknown significance (c.869C > T, p.Ala299Val) was identified in DNA from the Tampico Giant. The prevalence of AIP mutations in young Mexican patients with acromegaly is similar to that of European cohorts. Our results support the need for genetic evaluation of patients with early onset acromegaly.