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metachromatic leukodystrophy ( mld ) ( scholz 's disease ) is an autosomal recessive lysosomal storage disease caused by the lack of arylsulfatase a ( asa ) .
this enzyme is essential for the normal metabolism of sulfatides which are vital elements of the myelin sheath . in mld
, sulfatides accrue in many organs comprising brain , peripheral nerves , kidneys , liver , and gallbladder .
sulfatide collects in white matter of the central nervous system and peripheral nerves and causes progressive demyelination and lethal neurological symptoms .
mld is diagnosed biochemically by finding low levels of arylsulfatase in peripheral white blood cells and urine .
mld is classified into three main clinical forms on the basis of the age of onset .
the most common and lethal form is the late - infantile form , which begins before 4 years of age typically presenting between 12 and 18 months of age , and patients die by the end of the first decade .
the juvenile form of mld comprises age onset between 4 and 16 years , whereas symptoms of adult mld begin after puberty .
the patients usually present with signs and symptoms of peripheral neuropathy and alterations in intelligence , speech , and coordination .
the disorder is progressive with gait disturbance , quadriplegia , decerebration , and mortality by the age of 6 months to 4 years .
magnetic resonance ( mr ) imaging findings of the brain , especially t2-weighted imaging findings in the form of symmetric t2 hyperintense signal in the periventricular white matter , have been commonly reported in previous reports .
however , diffusion - weighted imaging ( dwi ) findings have been sparsely reported and we present mr imaging , especially dwi findings in a 12-month - old patient of mld .
a 12-month - old male presented with regression of milestones and progressive spasticity . mr imaging examination was performed and t2-weighted images revealed symmetrical hyperintensities , predominantly involving the deep white matter , corpus callosum with sparing of subcortical u - fibers [ figure 1 ] .
the tigroid and  leopard skin  patterns of demyelination , which imply sparing of the perivascular white matter , were evident in the periventricular white matter and centrum semiovale [ figure 2 ] .
the corpus callosum ( genu and splenium ) was also involved . using the transverse single - shot echo planar diffusion - weighted mr imaging ,
diffusion mr images were acquired . on b = 1000 mm / s images ( heavily dwis ) , hyperintensities were apparent in the deep white matter and corpus callosum with a signal intensity pattern the same as that of cytotoxic edema . on apparent diffusion coefficient ( adc ) maps ,
low levels of arylsulfatase in peripheral white blood cells and urine confirmed the diagnosis of mld .
( a and b ) bilateral symmetrical butterfly - shaped t2 hyperintensities of the periventricular and deep white matter with relative sparing of the subcortical u - fibers sagittal t2-weighted image showing tigroid pattern of due to hypointense linear bands against the background of hyperintense white matter the corresponding lesions showing restricted diffusion with high diffusion - weighted ( a and b ) and low apparent diffusion coefficient signal ( c and d )
symmetric confluent areas of t2 hyperintense signal in the periventricular white matter with sparing of the subcortical u - fibers and with no enhancement in postcontrast images are the most frequent reported mr imaging findings of mld .
the tigroid and  leopard skin  patterns of demyelination are basically due to sparing of perivascular white matter and are visualized as dark spots or dark linear areas against a background of hyperintense white matter , giving the appearance of the skin of a leopard .
the disease process also commonly affects the corpus callosum , internal capsule , and corticospinal tracts .
the cerebellar white matter may also be affected and appears bright on t2-weighted images . in the advanced stage of mld ,
it has been reported that the diminished activity of asa leads to dysmyelination ( failure of myelin breakdown and reutilization ) .
the corresponding distribution of the lesions on t2-weighted image and dwi in the present case strongly implied that the lesions on dwi were directly linked to the disease process .
restricted diffusion ( cytotoxic edema ) was seen on the echo planar sequence as hyperintensities on heavily dwis ( b = 1000 s / mm ) and low adc values on adc maps [ figure 3 ] .
sener reported a similar diffusion mr imaging pattern on echo planar diffusion images of a patient with mld with unchanged pattern on 6-month follow - up .
phillips et al . also reported a similar pattern of restricted diffusion in patients of phenylketonuria which was hypothesized to be due to impaired myelination leading to reduced mobility of protons .
hence , in the present case of mld , the restricted diffusion pattern perhaps was consistent with some breakdown of the white matter secondary to impaired myelination , which results in restricted mobility of protons leading to a diffusion mr imaging pattern similar to that of cytotoxic edema . to conclude , we report diffusion mr imaging of mld done using the echo planar sequence which has been sparsely reported .
more diffusion mr imaging studies of dysmyelinating disorders might improve our interpretation of the imaging features of these diseases .
metachromatic leukodystrophy ( mld ) is caused by insufficiency of arylsulfatase a resulting in impaired myelination . 
 diffusion magnetic resonance ( mr ) imaging features of this disease have been rarely reported . 
 we report diffusion mr imaging of mld in a 12-month - old male who presented with regression of milestones and progressive spasticity .