Molecular diagnosis of Velocardiofacial Syndrome in a cohort of Sri Lankan patients

Abstract

INTRODUCTION AND OBJECTIVES: Velocardiofacial Syndrome (VCFS) is caused by a 3 Mb deletion encompassing around 40 genes on chromosome 22qll.2. It is characterised by variable features including congenital malformations of the palate and heart, growth and developmental delay, immunological anomalies, hypocalcaemia and other problems. Clinical diagnosis is difficult due to its variability within and between families. Early diagnosis enables appropriate management of the affected cases. Objective was to establish a reliable and cost effective molecular diagnostic test for VCFS. METHODS: Nineteen clinically suspected patients with palatal and facial features suggestive of VCFS from Lady Ridgeway Hospital, Colombo and the Teaching hospital, Karapitiya were recruited following informed consent and prior ethical clearance. A semi-quantitative multiplex poiymerase chain reaction (PCR) was established to identify the deletion using dosage analysis. The PCR assay was carried out using DNA from patients (P), unaffected person (N) and a positive control (with a FISH confirmed deletion} using STS markers within the deleted region and CFTR (Cystic Fibrosis Transmembrane Regulatory Conductance) control primers outside the deleted region. Following agarose gel electrophoresis the PCR products were quantified. A ratio of P: N of 0.5 was taken to indicate a deletion while a ratio of 1 indicated absence of the deletion. RESULTS: Among nineteen clinically suspected VCFS cases, five cases had the deletion. CONCLUSIONS: This semi-quantitative PCR assay was able to identify.deletions in clinically suspected patients. However further validation is required before its clinical usage.