Purpose or Case Report: Krabbe disease is an autosomal recessive leukodystrophy that presents clinically with regression of milestones, excessive irritability and inconsolable crying. The pathologic basis of the disease is due to abnormal myelin metabolism resulting from a deficiency in the galactocerebrosidase enzyme with subsequent white matter destruction.
Although optic atrophy is a classic presentation of Krabbe disease, we report two patients who are biological brothers presenting with optic nerve enlargement in addition to other typical MR imaging features of Krabbe disease, thereby confounding the initial diagnosis.

Krabbe disease, also known as globoid cell leukodystrophy, is a lysosomal function disorder which ultimately results in demyelination and dysmyelination of white matter.
Worldwide incidence of Krabbe disease has been shown to be 1 in 100 000-200 000, with 1 in 150 000 live births reported in Europe (1, 2). The incidence in the South African population has not been well established.

Case Report 1:
Patient 1 presented in February 2012 to the paediatric neurodevelopmental clinic at 7 months of age with excessive inconsolable crying, regression of milestones, numerous café au lait macules and large eyes. Birth history was non-contributory.
MRI of the brain was done, demonstrating hypertrophy of the optic nerves and multiple other cranial nerves bilaterally (see figure 1).
High signal intensities were noted within the white matter of the brachium pontis, cerebellar dentate nuclei and corona radiata with a significant background of cortical and white matter atrophy (see figure 2).

Patient 1 died at one year of age with a provisional diagnosis of Neurofibromatosis I (NFI). No specific tests for Krabbe disease were performed prior to his death.

Case Report 2:
Patient 2 presented in November 2014 at 5 months of age with regression of milestones, excessive crying which was difficult to soothe, numerous café au lait macules, large eyes and a relative macrocephaly. Birth history was non-contributory and the child developed normally up until 3 months of age.
Blood tests for amino acids and organic acids, as well as liver and renal functions were normal. CSF lactate and glycine levels were also normal.

Specific enzyme testing for Krabbe disease was performed for patient 2 in Philadelphia, United States. Results revealed the galactocerebrosidase enzyme value to be very low (0.07). This is in the range of patients affected with Krabbe disease.
Patient 2 died shortly after the diagnosis of Krabbe disease was confirmed.

MRI brain scan of patient 2 demonstrated markedly hypertrophied optic nerves (see figures 3 and 4). Increased T2 and T2 Flair signal intensities of the white matter of the brachium pontis and the cerebellar dentate nuclei (see figure 5). The midbrain, pons and cerebellum also demonstrated increased T2 and T2 Flair signal intensities with a significant background of cortical and white matter atrophy (see figure 6).

PLEASE NOTE: the discussion related to Krabbe disease in this case review has not been included here due to charachter limitations. In addition, 6 images in total will be included should this case report be accepted for presentaton.
Methods & Materials:
Results:
Conclusions: Optic atrophy is one of the clinical presenting features of Krabbe disease. However, in rare cases as we report, optic nerve enlargement may be an association. Considering the higher prevalence of Neurofibromatosis-I, one can easily be misled by these imaging features into making the diagnosis.
The early awareness of neuroimaging findings in Krabbe disease together with a suggestive clinical presentation will allow for timely management and genetic counseling to parents.