Table 3.

Select Features of Classic Isovaleric Acidemia

Feature% of Persons w/Feature
Identified by NBS 1Not identified by NBS
Early onset w/prompt diagnosisDelayed diagnosis (missed diagnosis or later onset)
Acute metabolic decompensations70% 290%-100% 380% 4
Seizures15% 1Prevalent 5Prevalent 5
Speech/language delay15%-20% 1, 625% 4Prevalent 5
Gross/fine motor delay5%-16% 1, 6Prevalent 4, 5Prevalent 5
Intellectual disability /
impaired cognition		10% 115%-18% 455%-56% 4
Muscular hypotonia5% 1Prevalent 4, 5Prevalent 5
Movement disorder15% 1Prevalent 4, 5Prevalent 5
Infantile mortality0% 133% 43% 4, 7

NBS = newborn screening

1.
2.

In those with classic IVA identified on newborn screening, 50% of decompensations occur in the neonatal period [Mütze et al 2021].

3.

In those with classic IVA not identified on newborn screening, most present with metabolic decompensation [Grünert et al 2012, Kölker et al 2015b].

4.
5.
6.
7.

This frequency is quite likely to be underestimated, as a relevant number of infants and children might have died without correct diagnosis.

From: Classic Isovaleric Acidemia

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