ABSTRACT
Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal disorder caused by deficiency of arylsulfatase A (ARSA), leading to an accumulation of sulfatides. Sulfatides have been quantified in urine, dried blood spots (DBS), and tissues of patients with MLD. Newborn screening (NBS) for MLD has already been proposed based on a two-tier approach with the quantification of sulfatides in DBS followed by the quantification of ARSA by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Prenatal screening for MLD is also crucial, and sulfatide quantification in amniotic fluid (AF) can aid diagnosis. The prenatal study was initiated due to a family history of MLD at 19 weeks of gestation. ARSA was quantified in cultured amniocytes. C16:0 sulfatide was quantified by LC-MS/MS in the supernatant of AF. Molecular analysis of the ARSA gene was performed in cultured amniocytes. ARSA was deficient in fetal cells, and C16:0 sulfatides were significantly elevated in comparison to age-matched controls (3-fold higher). Genetic studies identified the c.465+1G>A variant in homozygosis in the ARSA gene. Our study shows that sulfatides can be quantified in the supernatant of AF of MLD fetuses, and it could potentially aid in a faster and more accurate diagnosis of MLD patients.
ABSTRACT
The study of the fetal karyotype became an important tool for the fetal diagnosis of genetic diseases in the 1970s. Although application of this test has remained very restricted in Brazil, we had 905 referrals for prenatal fetal karyotyping between 1989 and 2007. In 879 cases, a fetal karyotype was obtained. We detected 74 abnormal karyotypes (8.4%), the majority being found when the prior indication was fetal malformation. When obtaining amniotic fluid or chorionic villus samples was difficult, alternative fetal materials (urine, cystic hygroma, cystic lung, intreperitoneal and cerebrospinal fluids) were collected and we had success in obtaining karyotypes in all 13 cases. Although, the option of terminating abnormal pregnancies does not legally exist in Brazil, the information gained in assessing the prognosis of on-going pregnancies or estimating recurrence risks justifies prenatal diagnosis of chromosome abnormalities. We conclude that, in keeping with the policy in most other countries, prenatal cytogenetic analysis is strongly recommended in high-risk pregnancies for fetal abnormalities. However, the unique aspect of this type of study is not its rarity in world terms, but its rarity in Brazil. This argues that Brazilian health policy on prenatal diagnosis requires reforming to make it much more widely available within the public health care sector.
