[A study of subtelomeric rearrangements in 300 patients with mental retardation and multiple congenital anomalies: their clinical and molecular characterisation].

INTRODUCTION: The study of mental retardation is one of the most complex fields in human genetics due to its high degree of clinical and genetic heterogeneity. About 50% of cases of mental retardation remain undiagnosed. It is known that about 6-10% of cases are due to subtelomeric rearrangements. Some of these are responsible for a clinically recognized phenotype, i.e. 1p36 or 22q13.33 microdeletion syndromes, but others affect few patients and are not well characterized. PATIENTS AND METHODS: We have analyzed 300 consecutive mentally retarded patients for subtelomeric rearrangements by MLPA.
RESULTS: About 5.3% of patients presented subtelomeric rearrangements; from these, 75% contained de novo rearrangements and 18.7% included inherited aberrations from a healthy parent. In 14 cases, aberrations were likely related to disease and in two cases were putative polymorphisms.
CONCLUSIONS: This study confirms the high frequency of subtelomeric rearrangements in mental retardation and reinforces the idea of a routine subtelomeric screening in these patients in order to get a correct diagnosis, establish genotype-phenotype correlations and offer an accurate genetic counseling.