Next generation sequencing in endocrine practice.

With the completion of the Human Genome Project and advances in genomic sequencing technologies, the use of clinical molecular diagnostics has grown tremendously over the last decade. Next-generation sequencing (NGS) has overcome many of the practical roadblocks that had slowed the adoption of molecular testing for routine clinical diagnosis. In endocrinology, targeted NGS now complements biochemical testing and imaging studies. The goal of this review is to provide clinicians with a guide to the application of NGS to genetic testing for endocrine conditions, by compiling a list of established gene mutations detectable by NGS, and highlighting key phenotypic features of these disorders. As we outline in this review, the clinical utility of NGS-based molecular testing for endocrine disorders is very high. Identifying an exact genetic etiology improves understanding of the disease, provides clear explanation to families about the cause, and guides decisions about screening, prevention and/or treatment. To illustrate this approach, a case of hypophosphatasia with a pathogenic mutation in the ALPL gene detected by NGS is presented.

Severe Congenital Hypothyroidism Due to a Novel Deep Intronic Mutation in the TSH Receptor Gene Causing Intron Retention.

In 3 Somalian siblings with severe nongoitrous congenital hypothyroidism, exome sequencing identified a variant in TSHR predicted to be benign in isoform 3 but leading to an intronic mutation in isoform 1 (NM_00369:c.692 + 130C>A), which is the isoform expressed in the thyroid. This mutation creates a pseudoexon that results in a protein that, if transcribed, would lack the transmembrane domain, thereby hampering its expression at the cell surface. Our findings illustrate that the interpretation of exome analysis requires knowledge of the relevant isoform expression and of the biology of the disease. This is the first description of a deep intronic mutation creating a pseudoexon and inactivating the thyroid stimulating hormone (TSH) receptor.

Case Report: The Specter of Untreated Congenital Hypothyroidism in Immigrant Families.

Newborn screening has dramatically reduced rates of untreated congenital hypothyroidism (CH). However, in low-income nations where newborn screening programs do not exist, untreated CH remains a significant health and societal challenge. The goal of this report is to alert health care providers about the potential of undiagnosed CH in unscreened immigrant children. We report 3 siblings of Somali descent with CH who started treatment with levothyroxine at age 0.5 years, 7.7 years, and 14.8 years and were followed for 8 years. This case series demonstrates a spectrum of severity, response to treatment, and neurocognitive and growth outcomes depending on the age at treatment initiation. Patient 1, now 22 years old, went undiagnosed for 14.8 years. On diagnosis, his height was -7.5 SDs with a very delayed bone age of -13.5 SDs. His longstanding CH was associated with empty sella syndrome, static encephalopathy, and severe musculoskeletal deformities. Even after treatment, his height (-5.2 SDs) and cognitive deficits remained the most severe of the 3 siblings. Patient 2, diagnosed at 7.7 years, had moderate CH manifestations and thus a relatively intermediate outcome after treatment. Patient 3, who had the earliest diagnosis at 0.5 years, displayed the best response, but continues to have residual global developmental delay. In conclusion, untreated CH remains an important diagnostic consideration among immigrant children.

Bilateral mental nerve neuropathy in an adolescent during sickle cell crises.

Mental nerve neuropathy causes the "numb chin" syndrome and is usually associated with mandibular bone injury or disease in adults. It has been reported in adults during sickle cell crises. We describe a 15-year-old boy who developed bilateral mental nerve neuropathies during a sickle cell crisis. This case is unusual because of the simultaneous bilateral involvement and because of the age.