Demonstration of specific storage material within cutaneous nerves in metachromatic leukodystrophy

Biopsies of clinically unaltered skin from a 5-year-old girl with metachromatic leukodystrophy were studied by light, fluorescence and analytical electron microscopy. Investigation of hematoxylin-eosin-stained sections revealed no pathologic changes, but a brown metachromatic material was found within cutaneous nerves after acetic acid cresyl violet staining of frozen sections. In semithin Epon sections small dermal nerve fascicles contained endoneural deposits, which proved to correspond with the typical prismatic, dense or Tuffstein bodies described in other organs of patients suffering from MLD. The inclusions were located mainly within Schwann cells and exhibited a bright orange fluorescence after trypaflavine-phosphotungstic acid-treatment as well as a high electron density in serial ultrathin sections. Energy dispersive X-ray microanalysis revealed a high sulfur content in the membrane bound granules. These findings demonstrate the presence of the specific storage material also within cutaneous nerves in MLD and thus suggest skin biopsies as an addiitonal and simple diagnostic acid in this disease.