Sandhoff disease in Cyprus: population screening by biochemical and DNA analysis indicates a high frequency of carriers in the Maronite community.

In the last 15 years, four patients with the infantile form of Sandhoff disease were diagnosed in four different families in Cyprus (population 703,000, birth rate 1.7%). Three of these cases came from the Christian Maronite community (less than 1% of the population) and one from the Greek community (84% of the population). This relatively large number of patients prompted us to initiate an epidemiological study in order to establish the frequency of the mutant allele in Cyprus. Carrier detection was initially based on the measurement of beta-hexosaminidase A and B in both leucocytes and serum. Using the enzyme test, 35 carriers were identified among 244 random Maronite samples and 15 among 28 Maronites with a family history of Sandhoff disease, but only one carrier was found out of 115 random samples from the Greek community. In parallel to the biochemical screening, DNA studies were undertaken in one of the three Maronite patients and in a Greek carrier related to the Greek patient. These studies resulted in the identification of two novel mutations, a deletion of A at nt76 and a G to C transversion at position 5 of the 5'-splice site of intron 8, which have been published. We subsequently screened the carriers detected in the biochemical study for these two mutations using PCR-based tests. Of 50 Maronite carriers examined, 42 were found to have the nt76 deletion. Eight Maronite samples, designated carriers from the biochemical results, were negative for both mutations. It is possible that these individuals were incorrectly classified as carriers since their enzyme values are equivocal, although the presence of another mutation has not been excluded. Two Greek Cypriot carriers and two obligate Lebanese carriers were negative for both mutations. We conclude that there is a high frequency of Sandhoff disease carriers in the Maronite community of Cyprus, approximately 1 in 7, and that a single mutation predominates in this population.

Neonatal screening for Duchenne muscular dystrophy: a novel semiquantitative application of the bioluminescence test for creatine kinase in a pilot national program in Cyprus.

The objectives of this study were to evaluate a novel semiquantitative application of the bioluminescence test for screening newborns for Duchenne muscular dystrophy (DMD) and to use this technique in a pilot national program. The study was performed on the island of Cyprus, which provides ideal conditions for maximizing the prevention rate due to the small size of the country, the well-defined population, and the high degree of awareness of the public concerning genetic diseases. Guthrie spots were obtained through the national screening center for phenylketonuria and congenital hypothyroidism. The bioluminescence method for measuring creatine kinase (CK) in dried blood spots was adapted for use in a semiquantitative way. During the first 6 years of the program (1992-1997), we screened 30,014 samples and found 43 with initially high CK values. We were able to obtain repeat specimens in 35 cases. Of the repeat samples, 30 were found to have normal activity, giving a false-positive rate of 0.10%. Five boys had persistent CK elevations and were confirmed to be DMD or Becker (BMD) cases by DNA analysis and/or dystrophin analysis. The semiquantitative application of the bioluminescence assay of CK that we have introduced has proved to be a fast and reliable method for screening large numbers of samples for DMD. It has a low rate of false positives, which compares favorably with that of other DMD screening programs. Although it is early to evaluate its impact fully, the program seems to be bringing about the anticipated benefits to affected families.