Translation of a research-based genetic test on a rare syndrome into clinical service testing, with sotos syndrome as an example.

BACKGROUND AND AIMS: It is often the case that the genetic background of a rare disease has been solved, but the testing of a clinical patient can be performed only through research projects. Translating a research-based test into diagnostic service may also appear laborious and costly. Based on our molecular research of the genetics of Sotos syndrome, we developed a clinical laboratory test that is both effective and relatively inexpensive. METHODS AND RESULTS: Pilot testing was performed with samples of clinically diagnosed Sotos cases (n=13), and testing was continued with samples of patients who were suspected of having Sotos syndrome (n=161). The testing methods used were direct sequencing and multiplex ligation-dependent probe amplification. Sotos syndrome was a suitable example for test translation, because its genetic background was well established, and the demand for the test was expected to be fairly high. In the pilot phase, a mutation was detected in 12 out of 13 patients (92%), and in the second group, 49 out of 161 (30%) patients had a mutation in the NSD1 gene. CONCLUSIONS: In Sotos syndrome, detecting the mutation is valuable for the patient/family, while the value of a negative result is less clear and other differential diagnostic diagnoses should be considered. For successful translation of the research-based test into routine diagnostics, intense collaboration between clinicians, researchers, and diagnostic laboratory personnel is essential.

A familial CHARGE syndrome with a CHD7 nonsense mutation and new clinical features.

The autosomal dominant CHARGE syndrome (MIM musical sharp214800) is caused by mutations in the CHD7 gene. It is usually sporadic but a few cases with gonadal mosaicism and familial inheritance have been reported. We describe a familial CHARGE syndrome in a two-generation Finnish family with a nonsense mutation in the CHD7 gene. Detailed clinical examination of the affected family members was performed, and mutations in the CHD7 gene were analysed with direct sequencing and multiplex ligation-dependent probe amplification. A nonsense mutation, p.Q1599X, was detected in exon 21 of the CHD7 gene in three affected family members. The father was only mildly affected, whereas his son had a very severe manifestation of the syndrome, causing death at the age of 3 months. The second pregnancy was prematurely terminated in the 23rd week because of cardiac anomalies detected in the ultrasound scan. The father's brother also had mild symptoms, but no mutation was detected in him. In this report, the variability of clinical symptoms within families and the clinical importance of mildly affected patients with the CHARGE syndrome are underlined with implications for molecular genetic diagnostics of the syndrome. Features not described in the CHARGE syndrome before are also presented.