Nicola Tufton, Lucy Shapiro, Anju Sahdev, Ajith V Kumar, Lee Martin, William M Drake, Scott A Akker, and Helen L Storr
Phaeochromocytomas (PCC) and paragangliomas (PGL) are rare in children. A large proportion of these are now understood to be due to underlying germline mutations. Here we focus on succinate dehydrogenase subunit B (SDHB) gene mutation carriers as these tumours carry a high risk of malignant transformation. There remains no current consensus with respect to optimal surveillance for asymptomatic carriers and those in whom the presenting tumour has been resected.
We undertook a retrospective analysis of longitudinal clinical data of all children and adolescents with SDHB mutations followed up in a single UK tertiary referral centre. This included index cases that pre-dated the introduction of surveillance screening and asymptomatic carriers identified through cascade genetic testing. We also conducted a literature review to inform a suggested surveillance protocol for children and adolescents harbouring SDHB mutations.
Clinical outcomes of a total of 38 children are presented: 8 index cases and 30 mutation-positive asymptomatic carriers with 175 patient years of follow-up data. Three of the eight index cases developed metachronous disease and two developed metastatic disease. Of the 30 asymptomatic carriers, 3 were found to have PGLs on surveillance screening.
Surveillance screening was well tolerated in our paediatric cohort and asymptomatic paediatric subjects. Screening can identify tumours before they become secretory and/or symptomatic, thereby facilitating surgical resection and reducing the chance of distant spread. We propose a regular screening protocol commencing at age 5 years in this at-risk cohort of patients.
Sumana Chatterjee, Emily Cottrell, Stephen J Rose, Talat Mushtaq, Avinaash V Maharaj, Jack Williams, Martin O Savage, Louise A Metherell, and Helen L Storr
The homozygous GH receptor (GHR) pseudoexon (6Ψ) mutation leads to growth hormone insensitivity (GHI) with clinical and biochemical heterogeneity. We investigated whether transcript heterogeneity (6Ψ-GHR to WT-GHR transcript ratio) and/or concurrent defects in other short stature (SS) genes contribute to this.
6Ψ-GHR and WT-GHR mRNA transcripts of four 6Ψ patients (height SDS −4.2 to −3.1) and one control fibroblast were investigated by RT-PCR. Transcripts were quantified by qRT-PCR and delta delta CT analysis and compared using ANOVA with Bonferroni correction. In eleven 6Ψ patients, 40 genes known to cause GHI/SS were analysed by targeted next generation sequencing.
RT-PCR confirmed 6Ψ-GHR transcript in the 6Ψ patients but not in the control. 6Ψ-GHR transcript levels were comparable in patients 1 and 3 but significantly different among all other patients. The mean 6Ψ:WT transcript ratios ranged from 29–71:1 for patients 1–4 and correlated negatively with height SDS (R = −0.85; P < 0.001). Eight deleterious variants in six genes were detected, but the number of gene hits did not correlate with the degree of SS in individual 6Ψ patients.
Variable amounts of 6Ψ- and WT-GHR transcripts were identified in 6Ψ patients but no 6Ψ transcript was present in the control. Higher 6Ψ:WT-GHR transcript ratio correlated with SS severity and may explain the phenotypic variability. Analysis of known SS genes suggested that phenotypic variation is independent of the genetic background. This is the first report of transcript heterogeneity producing a spectrum of clinical phenotypes in different individuals harbouring an identical homozygous genetic mutation.