Neurometabolic disorder with microcephaly, dystonia, and central cyanosis masquerading as cerebral palsy.

Many neurodegenerative diseases can be misdiagnosed as cerebral palsy. The correct diagnosis is reached when the condition recurs in families or when there are specific clinical signs. The clinical and imaging features of 3 children, from 2 unrelated families, presenting with global developmental delay and dystonia are described, in whom the presence of cyanosis and methemoglobinemia confirmed the diagnosis of recessive hereditary methemoglobinemia type 2. Magnetic resonance imaging showed significant cerebellar atrophy in 2 of the 3 babies. In dark-skinned children, this condition is underdiagnosed, as mild cyanosis is difficult to detect. Screening for methemoglobinemia in children with dystonia, microcephaly, and progressive cerebellar atrophy can be helpful in identifying more cases. As there is no curative treatment for this autosomal recessive condition, the exact diagnosis offers the best chance for prenatal screening, by detecting deficient NADH--cytochrome b5 reductase enzyme activity or by identifying the specific mutation in cultured amniotic fluid cells.