Tuberous sclerosis complex (TSC) and nail-patella syndrome (NPS) are autosomal dominant pleiotropic disorders with full penetrance that can both involve kidneys. TSC1 and NPS genes are located on chromosome 9q3. In a large family with the two disorders with two novel frameshift TSC1 and LMX1B mutations, we describe the phenotypes. The father, who has both disorders, has passed on TSC to three of his children, NPS to another three, and both TSC and NPS to one child. Patients carrying both mutations appear to show an additive phenotype and no obvious epistatic effects. The segregation of two dominant disorders in this family poses a challenge for genetic counseling and indicates the importance of a careful clinical and molecular evaluation for accurate risk assessment.