ERDHEIM-CHESTER-DISEASE - LOW LOW-DENSITY-LIPOPROTEIN LEVELS DUE TO RAPID CATABOLISM

We have identified a 44-year-old patient with symmetrically excessive xanthomatosis, called Erdheim-Chester disease (ECD), and simultaneousl y decreased levels of low-density lipoprotein (LDL) cholesterol. Clini cally, this patient presents lipoidgranulomatosis of numerous long and flat bones with involvement of the liver, spleen, pericardium, pleura , thyroid, skin, conjunctiva, and gingiva. However, the patient does n ot have any signs of atherosclerosis. So far, the underlying defect ha s not been elucidated, We performed a LDL-apolipoprotein B (apoB) kine tic study in the ECD patient and a normal control to determine the eti ology of the low LDL level in ECD. LDL was isolated from both subjects , radioiodinated with either I-131 or I-125, and injected simultaneous ly into the ECD patient and the normal control. Normal and ECD LDL was catabolized at the same rate after injection into the control subject (fractional catabolic rate [FCR], 0.43/d and 0.46/d, respectively). T herefore, LDL isolated from an ECD subject is metabolically normal, In contrast, autologous LDL injected into the ECD subject showed a marke dly increased catabolism (FCR, 0.69/d) compared with that in the contr ol subject (FCR, 0.43/d). This is the first report about increased cat abolism of LDL cholesterol in a patient.