MALIGNANT OSTEOPETROSIS(OP): OBSERVATIONS ON THE DISEASE SPECTRUM

7 patients (pts) with OP (4 infants ages 0.3-0.6 yrs and 3 children ages 2.0-3.8 yrs) were studied biochemically and by bone biopsy to correlate laboratory parameters with disease outcome. All pts presented in the first 6 mo of life with optic atrophy, cranial n. dysfunction, respiratory abnormalities, and pallor. Distinguishing features are summarized below: Two infants (with advanced fibrosis) received massive doses (24 ug/d) of 1,25-(OH)2D3 for 3 weeks without bone biopsy improvement despite hydroxyprolinuria. Three infants and 1 child underwent bone marrow transplantation. Bony remodeling occurred in 1 infant and 1 child. Of the 2 infants with advanced fibrosis, 1 was evaluable and had engraftment in the nonfibrotic, membranous bone but not in the fibrotic endochondral bone. We conclude that the above parameters may correlate with bone biopsies and that advanced fibrosis may be predictive of resistence to therapies.