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Progressive Mitochondrial Leukoencephalopathy in a one and half year-old boy: A Case Report

Introduction Leukodystrophies are disorders of the white matter, caused by different genetic disorders affecting the oligodendroglial cells or the myelin. A new class of mitochondrial diseases presenting with leukodystrophy and multiple respiratory chain disorders have been classified as multiple mitochondrial dysfunction syndrome (MMDS) . There are four classes of MMDS: MMDS1 due to mutations in NFU1, MMDS2 with mutations in BOLA3 , MMDS3 with mutations in IBA57 and MMDS4 with mutations in ISCA2. All these MMDS involve a gene coding for a protein involved in the mitochondrial Fe/S cluster assembly. We present an interesting case of a toddler boy who was diagnosed with MMDS-3. Case A 18 month old baby boy born out of a non-consanguineous marriage, presented with subacute regression of milestones in all domains. Prior birth & development was normal. On examination, he had spastic dystonic hyperreflexic quadriparesis. MRI brain showed diffuse cavitating leukodystrophy involving bilateral periventricular white matter, centrum semiovale and corona radiata (figure 1) . MRS revealed a lactate peak (figure 2). Serum lactate levels were also elevated. Genetic studies revealed a compound heterozygous, autosomal recessive mutation in IBA57 gene, suggestive of MMDS- 3. Mitochondrial cocktail was started. Patient’s clinical condition had stabilized on follow up after 6 months, he had also regained a few milestones. Conclusion This case illustrates a rare mitochondrial encephalopathy called MMDS3 caused by IBA57 gene mutation. A high index of suspicion for a mitochondrial etiology should be maintained in a case of neuroregression with bilaterally symmetric cavitating leukodystrophy on MRI.