The oculocerebrorenal syndrome of Lowe is a rare X-linked multisystemic disorder characterized by the triad of congenital cataracts, cognitive and behavioral impairment and a renal proximal tubulopathy in almost all of the patients. Whereas the ocular manifestations and severe hypotonia are present at birth, the renal involvement appears within the first months of life. Patients show progressive growth retardation and may develop a debilitating arthropathy. Treatment is symptomatic and life span rarely exceeds 40 yr. The causative OCRL gene, encodes an inositol polyphosphate 5-phosphatase. OCRL mutations were not only found in classic Lowe syndrome, but also in milder affected patients, classified as having Dent-2 disease. There is a phenotypic continuum within patients with Dent-2 disease and Lowe syndrome, suggesting that there are individual differences in the ability to compensate for loss of enzyme function. Researchers have conducted a large amount of work to understand the etiology responsible for the disease. However, the mechanisms leading to the clinical manifestations are still poorly understood and we are far from an effective therapy. In this review, we have included well-established findings and the most recent progress in understanding Lowe syndrome and Dent-2 disease.