ß-Thalassemia in Pakistan: a pilot program on prenatal diagnosis in Multan.

Prenatal diagnosis (PND) of ß-thalassemia has been underutilized in Pakistan because of a number of social and economic factors. National Institute for Biotechnology and Genetic Engineering Faisalabad in collaboration with Multan Institute of Nuclear Medicine and Radiotherapy Multan introduced free PND service for carrier couples of Multan district. Multan has a population of about 4 million. More than 170 couples registered for retrospective PND and in 2 years 105 PND were carried out through first trimester chorionic villus sampling. Almost 90% of these couples were unable to afford the cost of PND and would not have undergone the test as free service was not available. Monoplex and Multiplex Amplification Refractory Mutation System-polymerase chain reaction and genomic DNA sequencing were used for detection of IVS (intervening sequence)-I-5 (G-C), FSC (frameshift codon)-8/9 (+G), FSC-41/42 (-TTCT), IVS-I-1 (G-T), 619 bp deletion, and CD-15 (G-A) ß-globin mutations. Eighty-one percent (85/105) couples analyzed were in a consanguineous marriage. Twenty-three fetuses were found homozygous mutant and all couples opted for discontinuation of affected pregnancies. More families are registering for PND after establishment of this free and accessible PND service.

Compound heterozygous ASPM mutations in Pakistani MCPH families.

Autosomal recessive primary microcephaly (MCPH) is characterized by reduced head circumference (50% of all reported families. In spite of the high frequency of MCPH in Pakistan only one case of compound heterozygosity for mutations in ASPM has been reported yet. In this large MCPH study we ascertained 37 families including 319 persons (140 patients). Haplotype analysis of eight STS markers suggested linkage by homozygosity in 20 families, and re-analysis of single sib ships in the remaining families demonstrated possible compound heterozygosity in two families. Direct sequencing indeed confirmed compound heterozygosity in two and homozygous mutations in 20 families, respectively, showing that up to 10% of families with MCPH caused by ASPM are compound heterozygous. In total we identified 16 different nonsense or frameshift mutations of which 12 were novel thereby increasing the number of mutations in ASPM significantly from 35 to 47. We found no correlation between the severity of the condition and the site of truncation. We suggest that the high frequency of compound heterozygosity observed in this study is taken into consideration as part of future genetic testing and counseling in Pakistani MCPH families.