Sea-blue histiocytes and sural nerve in neurovisceral storage disorder with vertical ophthalmoplegia.
Ultrastructural investigation of bone marrow histiocytes in neurovisceral storage disorder associated with vertical ophthalmoplegia revealed 3 types of cytosomes: (1) lamellar cytosomes; (2) larger cytosomes composed of lamellar fragments and a granular component; and (3) large irregular cytosomes with amorphous and granular portions, often including fingerprint profiles--in some of these, lysosome-like bodies were numerous. The lamellar cytosomes corresponded to vacuoles seen by light microscopy. The Type 2 and 3 cytosomes were the ultrastructural substract of Wright-Giemsa stained blue granules. Histiocytes having a predominance of Type 2 cytosomes in a cytoplasm rich in free ribosomes had the appearance of sea-blue histiocytes at the light-microscopic level. Transformed Type 1 cytostomes served as building blocks for Type 2 and 3 cytosomes. In the sural nerve, Schwann cells and endoneurial fibroblasts accumulated autofluorescent lipopigment but no lamellar cytosomes or their fragments were found on electron-microscopic examination. Ultrastructure of sea-blue histiocytes in this disease differed from that observed in some other diseases.