During the follow-up of cystinosis patients under protocol #78-HG-0093 "Use of Cysteamine in the Treatment of Cystinosis", we found that 6 of our NIH patients developed papilledema and were diagnosed with pseudotumor cerebri (PTC), whose occurrence has not been previously reported in cystinosis. The goal of this protocol is to identify the role of thrombosis susceptibility in the development of PTC in nephropathic cystinosis patients in view of our recent findings regarding genetic susceptibility to thrombosis in PTC in general. We propose a case-control study. A total of 9 nephropathic cystinosis patients who developed PTC and 9 control nephropathic cystinosis patients without PTC will be screened based upon a thrombosis susceptibility screening panel, including total homocysteine, protein C and S, antithrombin III, fibrinogen, Factor VIII, Factor IX, Factor XI levels, testing for PT, PTT, activated protein C resistance, antiphospholipid antibodies (ACA panel and Lupus AC) and screening for FV Leiden mutation, FV G1628A polymorphism, FV R2 allele, Prothrombin 20210 mutation and 5,10-methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism in patients with severe homocysteinemia (greater than or equal to 100 micro mol/l). We will compare the prevalence of the factors that lead to thrombosis susceptibility in the cases and controls.
* INCLUSION CRITERIA: The inclusion criteria include only a confirmed diagnosis of pseudotumor cerebri (past or present) in a patient with nephropathic cystinosis. Patients will be diagnosed as having pseudotumor cerebri based upon modified Dandy criteria: 1. signs and symptoms related to increased intracranial pressure; 2. no localizing neurological signs with the exception of unilateral or bilateral sixth nerve palsy; 3. neuroimaging study showing no mass lesion or hydrocephalus; 4. elevated opening pressure with normal cerebrospinal fluid contents on lumbar puncture. Nephropathic cystinosis patients of all ages who meet the Dandy criteria for PTC will be considered for the study. EXCLUSION CRITERIA: Pregnant patients will be excluded from the study.