RESUMO
BACKGROUND AND PURPOSE: In chronic progressive spasticity of the legs many rare causes have to be considered, including leukodystrophies due to neurometabolic disorders. To determine the frequency of leukodystrophies and the phenotypic spectrum patients with cryptic spasticity of the legs were screened for underlying neurometabolic abnormalities. METHODS: Seventy-six index patients presenting with adult-onset lower limb spasticity of unknown cause consistent with autosomal recessive inheritance were included in this study. Screening included serum levels of very long chain fatty acids for X-linked adrenoleukodystrophy/adrenomyeloneuropathy and lysosomal enzyme activities in leukocytes for metachromatic leukodystrophy, GM1-gangliosidosis, Tay-Sachs, Sandhoff and Krabbe disease. If clinical evidence was indicative of other types of leukodystrophies, additional genetic testing was conducted. Clinical characterization included neurological and psychiatric features and magnetic resonance imaging. RESULTS: Basic screening detected one index patient with metachromatic leukodystrophy, two patients with Krabbe disease and four patients with adrenoleukodystrophy/adrenomyeloneuropathy. Additional genetic testing revealed one patient with vanishing white matter disease. These patients accounted for an overall share of 11% of leukodystrophies. One patient with Krabbe disease and three patients with adrenoleukodystrophy/adrenomyeloneuropathy presented with pure spasticity of the lower limbs, whilst one patient each with Krabbe disease, metachromatic leukodystrophy and adrenoleukodystrophy/adrenomyeloneuropathy showed additional complicating symptoms. CONCLUSIONS: Adult patients presenting with cryptic spasticity of the legs should be screened for underlying X-linked adrenoleukodystrophy/adrenomyeloneuropathy and lysosomal disorders, irrespective of the presence of additional complicating symptoms. Leukodystrophies may manifest as late as the sixth decade and hyperintensity of cerebral white matter on magnetic resonance FLAIR images is not obligatory.