An accurate diagnosis is an integral component of patient care for children with rare genetic disease. Recent advances in sequencing, in particular whole‐exome sequencing (WES), are identifying the genetic basis of disease for 25–40% of patients. The diagnostic rate is probably influenced by when in the diagnostic process WES is used. The Finding Of Rare Disease GEnes (FORGE) Canada project was a nation‐wide effort to identify mutations for childhood‐onset disorders using WES. Most children enrolled in the FORGE project were toward the end of the diagnostic odyssey. The two primary outcomes of FORGE were novel gene discovery and the identification of mutations in genes known to cause disease. In the latter instance, WES identified mutations in known disease genes for 105 of 362 families studied (29%), thereby informing the impact of WES in the setting of the diagnostic odyssey. Our analysis of this dataset showed that these known disease genes were not identified prior to WES enrollment for two key reasons: genetic heterogeneity associated with a clinical diagnosis and atypical presentation of known, clinically recognized diseases. What is becoming increasingly clear is that WES will be paradigm altering for patients and families with rare genetic diseases.

Estimating the incidence of CH is influenced by minimal changes in TSH screening cutoffs. Lower cutoffs identify additional cases that have predominantly functional disorders whose impact on intellectual disability, if left untreated, remains to be determined.

Four distinct familial types of isolated GH deficiency have been described so far, of which type II is the autosomal dominant inherited form. It is mainly caused by mutations within the first 6 bp of intervening sequence 3. However, other splice site and missense mutations have been reported. Based on in vitro experiments and transgenic animal data, there is strong evidence that there is a wide variability in phenotype in terms of the severity of GH deficiency. Therefore, we studied a total of 57 subjects belonging to 19 families suffering from different splice site as well as missense mutations within the GH-1 gene. The subjects presenting with a splice site mutation within the first 2 bp of intervening sequence 3 (5'IVS +1/+2 bp) leading to a skipping of exon 3 were found to be more likely to present in the follow-up with other pituitary hormone deficiencies. In addition, although the patients with missense mutations have previously been reported to be less affected, a number of patients presenting with the P89L missense GH form, showed some pituitary hormone impairment. The development of multiple hormonal deficiencies is not age dependent, and there is a clear variability in onset, severity, and progression, even within the same families. The message of clinical importance from these studies is that the pituitary endocrine status of all such patients should continue to be monitored closely over the years because further hormonal deficiencies may evolve with time.

The incidence of CHTD did not vary over the observation period, and its monthly variation was random. Therefore, environmental factors do not appear to play a significant role in the etiology of CHTD.