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Pelizaeus Merzbacher disease

Dr Abhilash Sandhyala and Dr Yuranga Weerakkody et al.

Pelizaeus Merzbacher disease (PMD) is an X-linked leukodystrophy which is characterised by an arrest in myelin development.

Clinical presentation

Patients may present with

pendular eye movements
hypotonia
pyramidal disease

Pathology

Genetics

It occurs from a derangement in the proteolipidprotein (PLP1) gene locus at Xq22. This can be either a mutation, deletion or duplication (commonest) ⁴.

Sub types

Traditionally divided into 2 sub types

classic
connatal : rarer and more severe ⁵.

Radiographic features

CT

Non specific and may show hypo attenuating white matter with progressive white matter atrophy.

MRI

The lack of myelination is often seen as high T1 signal regions typically involving internal capsule, proximal corona radiata and the optic radiation and with near complete absence of expected low T2 signal in supra-tentorial region. signal abnormalites can either be diffuse or patchy. If there is patchy involvement, a characteristic tigroid appearance may be seen ⁵.

MR may also show cortical sulcal prominence.

MR spectroscopy : affected areas often show a reduction in the NAA peak ⁴.

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