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In the article “Teaching NeuroImages: A rare case of Jacobsen syndrome with global diffuse hypomyelination of brain,” Patel et al. presented MRI fluid-attenuated inversion recovery (FLAIR) images at 18 months and 3 years of age in a boy with Jacobsen syndrome due to an 11q23-11q24 deletion. The images showed improvement in white matter abnormalities, which were termed hypomyelination by the authors. In response, Wolf et al. argued that hypomyelination is a permanent myelin deficit and is associated with a less hyperintense T2 white matter signal than is seen in this patient. They noted that the patient's deletion encompasses HEPACAM, a gene for which haploinsufficiency is associated with leukodystrophy that improves with time. They noted that the case is representative of limitations in extant classifications of leukodystrophies as either hypomyelinating or demyelinating. Responding to these comments, Patel et al. agreed that HEPACAM loss of function may account for some of the imaging abnormalities in Jacobsen syndrome but noted that macrocephaly and cysts (classical findings with HEPACAM mutations) are not typically seen in this syndrome. They noted that the original neuroradiologist interpretation termed the findings as global diffuse hypomyelination. This exchange highlights current uncertainties in the terminology surrounding the white matter abnormalities, particularly in the pediatric population.
In the article “Teaching NeuroImages: A rare case of Jacobsen syndrome with global diffuse hypomyelination of brain,” Patel et al. presented MRI fluid-attenuated inversion recovery (FLAIR) images at 18 months and 3 years of age in a boy with Jacobsen syndrome due to an 11q23-11q24 deletion. The images showed improvement in white matter abnormalities, which were termed hypomyelination by the authors. In response, Wolf et al. argued that hypomyelination is a permanent myelin deficit and is associated with a less hyperintense T2 white matter signal than is seen in this patient. They noted that the patient's deletion encompasses HEPACAM, a gene for which haploinsufficiency is associated with leukodystrophy that improves with time. They noted that the case is representative of limitations in extant classifications of leukodystrophies as either hypomyelinating or demyelinating. Responding to these comments, Patel et al. agreed that HEPACAM loss of function may account for some of the imaging abnormalities in Jacobsen syndrome but noted that macrocephaly and cysts (classical findings with HEPACAM mutations) are not typically seen in this syndrome. They noted that the original neuroradiologist interpretation termed the findings as global diffuse hypomyelination. This exchange highlights current uncertainties in the terminology surrounding the white matter abnormalities, particularly in the pediatric population.
Footnotes
Author disclosures are available upon request (journal{at}neurology.org).
- Received January 10, 2020.
- Accepted in final form January 8, 2020.
- © 2020 American Academy of Neurology
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