Clinical onset and prognosis of Asian children with organic acidemias, as detected by analysis of urinary organic acids using GC/MS, instead of mass screening.

Organic acidemias (OAs) have been detected worldwide in symptomatic patients using gas chromatography mass spectrometry. We diagnosed 188 Asian cases of OAs by analysis of urinary organic acids and investigated their clinical onset and outcome. Methylmalonic acidemia (MMA) was most common (74 cases), followed by propionic acidemia (23 cases), ornitine transcarbamylase deficiency (22 cases), and multiple carboxylase deficiency (15 cases). For these 188 patients, onset was most frequent in the neonatal period or early infancy. Approximately 30% of the patients had a family history of similar symptoms or diseases. Although the outcome of OA patients varied, patients with early onset generally had poor outcomes despite early detection. Of the 45 MMA patients whose clinical data were available, 25 were clinically vitamin B12-responsive, while the remaining 20 were non-responsive. A favorable outcome was obtained in 7 of the 25 B12-responsive patients, and in only 3 of the 20 B12-nonresponsive patients. It was suggested that even in B12-responsive MMA cases, earlier detection and B12 therapy were needed to improve the prognosis. We concluded that detection of such patients at the presymptomatic stages using newborn mass screening is essential for prognosis improvement with OAs.

Mutations causing profound biotinidase deficiency in children ascertained by newborn screening in the United States occur at different frequencies than in symptomatic children.

Biotinidase deficiency is an autosomal recessive disorder of biotin metabolism that can lead to varying degrees of neurologic and cutaneous symptoms when untreated. Because this disorder meets the criteria for newborn screening, many states and countries perform this testing. Because newborn screening should result in complete ascertainment of mutations causing profound biotinidase deficiency (less than 10% of mean normal serum activity), we compared the mutations in a group of 59 children with profound biotinidase deficiency who were identified by newborn screening in the United States with 33 children ascertained by exhibiting symptoms. Of the 40 total mutations identified among the two populations, four mutations comprise 59% of the disease alleles studied. Two of these mutations occur in both populations, but in the symptomatic group at a significantly greater frequency. The other two common mutations occur only in the newborn screening group. Because two common mutations do not occur in the symptomatic population, it is possible that individuals with these mutations either develop mild or no symptoms if left untreated. However, inasmuch as biotin treatment is inexpensive and innocuous, it is still recommended that all children with profound biotinidase deficiency be treated.