Plasma fractionated free metanephrines measured by EIA have good sensitivity and specificity in the diagnosis of pheochromocytoma and catecholamine-secreting paraganglioma.

Background: Genetic aetiology of pheochromocytoma (PCC) and paraganglioma (PGL) is increasingly being studied; however, Asian Indian data on this aspect are scarce. Objective: To study the prevalence of germline mutations and genotype-phenotype correlation in Asian Indian PCC/ PGL patients. Design: In this study, 150 index patients (M:F, 73:77) with PCC/PGL were evaluated. Phenotypic data were collected. Germline mutations in five susceptibility genes (RET, VHL, SDHB, SDHD and SDHC) were tested by sequencing and NF1 was diagnosed according to phenotype. Result: Of the total population, 49 (32.7%) PCC/PGL patients had germline mutations (VHL: 23 (15.3%), RET: 13 (8.7%), SDHB: 9 (6%), SDHD: 2 (1.3%) and NF1: 2 (1.3%)). Amongst the 30 patients with familial and/or syndromic presentation, all had germline mutations (VHL: 14 (46.7%), RET: 13 (43.3%), SDHB: 1 (3.3%) and NF1: 2 (6.7%)). Out of 120 patients with apparently sporadic presentation, 19 (15.8%) had a germline mutation (VHL: 9 (7.5%), SDHB: 8 (6.7%) and SDHD: 2 (1.7%)). Mutation carriers were younger (29.9 ± 14.5 years vs 36.8 ± 14.9; P = 0.01) and had a higher prevalence of bilateral PCC (26.5% vs 2.9%, P < 0.001) and multifocal tumours (12.2% vs 0.96%, P = 0.06). Based on syndromic features, metastasis, location and number of tumours, around 96% mutations in our cohort could be detected by appropriately selected single gene testing. Conclusion: Asian Indians with PCC/PGL differ from Western cohorts in having preponderance of VHL mutations in multifocal tumours and apparently sporadic unilateral PCC. Syndromic presentation, metastasis, location and number of PCC/PGL can be effectively used for guiding genetic prioritisation.

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In our cohort, 60% were KS with majority of males and a severe reproductive phenotype as against nIHH. Contribution of the genetic burden for the five genes studied was 15·5%. RSV p.C279Y in GNRHR may have a founder effect originating from south Asia. This study provides a model for molecular and phenotypic representation of Asian Indian subjects with IHH.

The study suggests that the underlying genetic status determines FDG uptake in PCC/PGL and not location, secretory status or malignancy.