Clinical: a) The behavioral phenotype in the Oculocerebrorenal Syndrome of Lowe (OCRL) consists of 6 target maladaptive behaviors. Additional heterozygote and prenatal hemizygote abnormalities have been defined. b) The hazard rate of stroke, TIA, or brain abscess in patients with hereditary hemorrhagic telangiectasia and pulmonary arteriovenous malformation is on the order of 1.5% per year, one hundred times the rate in unaffected young persons. C) The distal myopathy of cystinosis is a vacuolar myopathy. d) Neurologic manifestations of osteogenesis imperfecta include increased head circumference, pseudoatrophy, basilar invagination, a substantial risk of skull fracture, and hydromyelia. e) At least 15% of patients referred to NIH for growth hormone therapy of "normal" very short children have unrecognized genetic causes for short stature. Laboratory: a) A mouse partial cDNA homolog of the human gene causing OCRL has been isolated. It is expressed in high level in specific neurons of the adult nervous system, including Purkinje cells, hippocampus, spinal cord gray matter, neural retina, and lens epithelium. b) In an amphibian system, the low molecular weight neurofilament protein XNF-L is organized the same as mammalian NF-L's, while XNIF has novel intron locations. By in situ hybridization, XNIF gene expression is first detected in single spinal cord neurons at Stage 22, while XNF-L gene expression is first detected at Stage 28. The relative abundance and order of expression of these two genes is similar, but 18-24 hours earlier than determined using antibody probes.