PRENATAL DIAGNOSIS OF SALLA DISEASE (SD)

Abstract

Salla disease (SD) is a lysosomal storage disease characterized by severe early onset psychomotor retardation and intralysosomal accumulation of free sialic acid (SA). Four pregnancies at risk for SD were monitored by quantitation of free and total SA in amniocytes and amniotic fluid, using a sensitive HPLC method. Three children, were normal. One child was affected. This child was born before SA had been discovered to be the storage compound in SD. Free SA was only slightly elevated in the amniotic supernatant fluid of the affected child (5.7 nmol/ml) as compared to the three unaffected (2.8, 3.3 and 3.5) and controls (1.7 to 5.7) and therefore could not be used for diagnostic purposes. Free SA content of the amniocytes from the affected child was 2.6 nmol/mg protein, which was about 5 times higher than the content in the three unaffected cases (0.3, 0.4 and 0.8, respectively) and 14 controls (0.3-0.9). The ratio of free /total SA of the amniocytes also clearly distinguished the affected pregnancy (0.138) from the unaffected (0.023-0.048) and controls (0.018-0.053). These findings represent the first successful prenatal diagnosis of SD and indicate that both amniocyte free S A and free/total SA ratio should be monitored in pregnancies at risk for SD.