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Megalencephalic leukoencephalopathy with subcortical cysts
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     Child Development and Early Intervention Clinic, Department of Pediatrics, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India

    We read with interest the case of megalencephalic leukoencephalopathy with subcortical cysts (MLC) reported by Sethi et al[1]. MLC is a recently described disorder of white matter which is increasingly being reported from India, especially in the particular ethnic group; the Agarwals.[2],[3] We diagnosed 4 cases of MLC during the last 1 year; one of them is an Aggarwal child and would like to share our experience.

    Case 1 was a 1-year-old female child, born at term from a non consanguineous marriage to parents belonging to the Rajput clan. She presented to us with developmental delay and enlarging head size noted since 5 months of age, without any history of seizures or features suggestive of raised intracranial tension. Examination revealed an alert child with normal facies. Head circumference was 50.8 cm (>95th centile). Systemic examination including fundus was normal. The Development Quotient (tested using Developmental Assessment Scale for Indian Infants) was 70. MRI revealed diffuse white matter swelling in the subcortical regions with sparing of central white matter Figure1a, b; the basal ganglia and thalami appeared normal Figure1b. Subcortical cysts were seen in the frontal and temporal lobes Figure1c. Molecular genetic testing (Courtesy: Dr Seiichi Tsujino, Japan) revealed a mutation, an insertion of C-residue in a stretch of 6 C-residues, in the exon 2 of the MLC 1 gene.

    Case 2 also presented similarly. This was a 1-year-old muslim boy who was brought with a history of mild developmental delay and large head noticed since 4 months of age. Examination other than macrocephaly was normal. MRI revealed diffuse white matter swelling, normal gray matter and subcortical cysts.

    Case 3 was an 8-year-old boy belonging to the Agarwal community, who presented to us with one episode of generalized tonic clonic seizure 1 month back without any focal deficit or intellectual deterioration. He was a student of Class 3, with a good academic performance. On examination, the head circumference was 55 cm, the rest of the examination was normal. MRI revealed features of MLC.

    Case 4 was a 5-year-old boy, belonging to the Chamar community who presented with gradually progressing ataxia noted since 2 years of age. He also had moderate mental retardation. On examination, he had macrocephaly, gait ataxia and brisk deep tendon reflexes. MRI revealed diffuse white matter swelling with central sparing, and temporal subcortical cysts.

    MLC is a white matter disorder that is remarkable for its mild neurological signs and symptoms in the setting of a very abnormal imaging study.[4] Its prominent features are onset during infancy, megalencephaly, a mild clinical course and typical MRI findings (diffuse homogenous supratentorial white matter abnormality with sparing of central white matter, the absence of gray matter involvement, and presence of subcortical cysts in temporoparietal region).[5] No biochemical defect has been identified so far.[3]

    Singhal et al have recently described a series of Indian patients with MLC, most of them Agarwals.[3] The authors also reported results of genetic testing in 31 patients with MLC belonging to the Agarwal community; and all showed the same homozygous mutation in the exon 2 of the MLC 1 gene. We could get genetic testing in 1 case (case 1), who also had this same mutation; though she does not belong to the Agarwal community. This may be a common mutation in Indian patients with MLC. The recent availability of molecular genetic testing allows confirmation of diagnosis and genetic counselling of patients and their families.

    References

    1. Sethi PK, Sethi NK. Megalencephalic leukoencephalopathy with subcortical cysts. Indian J Peditar 2004; 71: 473-475.

    2. Singhal BS, Gursahani RD, Udani VP, Biniwale AA. Megalencephalic leukodystrophy in an asian Indian group.

    3. Singhal BS, Goropse R, Naidu SN. Megalencephalic leukoencephalopathy with subcortical cysts. J Child Neurol 2003; 18: 646-652.

    4. Barkovich AJ. Pediatric Neuroimaging. 3rd edn. Philadelphia: Lippincott, Williams and Wilkins; 2000.

    5. van der Knaap MS, Bart BG, Stroin H, van Nieuwenhuizen O, Arts WFM, Hoogenraad F et al. Leucoencephalopathy with swelling and discrepantly mild clinical course in 8 children. Ann Neurol 1995; 37: 324-334.(Juneja Monica, Sharma Suv)