A 1-month-old Japanese infant with cardiac rhabdomyoma was diagnosed with TSC2/PKD1 contiguous gene syndrome by targeted panel sequencing with subsequent quantitative polymerase chain reaction that revealed gross monoallelic deletion, including parts of two genes: exons 19–42 of TSC2 and exons 2–46 of PKD1. Early molecular diagnosis can help to detect bilateral renal cyst formation and multidisciplinary follow-up of this multisystem disease. The gene discussed is PKD1; the disease is cardiac rhabdomyoma.