GALK1 and hyperinsulinemic hypoglycemia, familial, 4: As much as 40% of early-onset cataracts may have a genetic basis [2], either as a recognized feature of over 50 genetic syndromes, involving other ocular defects (e.g., microphthalmia) and systemic abnormalities (e.g., galactokinase deficiency), or more often as an isolated lens phenotype with autosomal dominant inheritance (Online Mendelian Inheritance in Man; OMIM).