Expert Opinion :
This child has neuroregression. He has no seizures and has spasticity suggestive of predominantly involvement of the pyramidal tracts i.e., the white matter. (Grey matter involvement would have seizures and encephalopathy, poor social behavior). In addition, the deep tendon reflexes are poor suggestive of a lower motor neuron lesion such as peripheral neuropathy. If the motor aspect of the LMN lesion was involved, the child would have flaccidity and hypotonia. Since spasticity is maintained but reflexes are sluggish, it suggests involvement of the sensory arc of the reflex system and hence peripheral neuropathy. In addition the child has nystagmus. Nystagmus may be due to cerebellar, vestibular or visual impairment. Cerebellar and vestibular causes would in addition have an unsteady child. In this child since visual fixation is poor, nystagmus would suggest visual impairment such as optic atrophy or optic tract defect or occipital lobe affection. (Optic neuritis would lead to pain and sudden onset blindness).
Thus, this child has neuroregression, while matter disease, peripheral neuropathy and visual defect. Thus most likely diagnosis in this child would be either
- Krabbe’s disease
- Metachromatic leukodystrophy (MLD)
- X-linked adrenoleukodystrophy (ALD).
MRI brain in this child showed severe white matter disease with involvement of U fibers suggestive of MLD. Funduscopy showed foveal hypoplasia (optic atrophy). NCV showed peripheral neuropathy and enzyme estimation for Arylsulphatase-B confirmed diagnosis of MLD.