Sulfatides, the most abundant glycosphingolipids, are a major component of myelin. They are degraded by the combined action of sphingolipid activator protein and arylsulfatase A. Deficiency of either of these entities causes metachromatic leukodystrophy (MLD). On the basis of age of onset, this entity is divided into late infantile, juvenile, and adult subtypes. Late infantile form, the commonest subtype, can exhibit peripheral neuropathy as the initial manifestation. The other two forms usually manifest peripheral neuropathy later in the disease course.

A 1.5-year-old girl with preexisting isolated motor delay presented with acute-onset ascending flaccid quadriparesis, ptosis, and respiratory failure. Ptosis and respiratory failure responded completely to intravenous immunoglobulin, whereas quadriparesis showed minimal improvement. Nerve biopsy revealed metachromatic granules with demyelination, and serum arylsulfatase A levels were undetectable.

The severity and nature of the disease coupled with the response to immunotherapy makes this case unusual. This child may represent either an atypical presentation of MLD with coincidental response to immunotherapy or an episode of immune mediated neuropathy in an individual with already diseased nerves due to MLD.