<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by van der Woude syndrome ? [/INST] Van der Woude syndrome is believed to occur in 1 in 35,000 to 1 in 100,000 people, based on data from Europe and Asia. Van der Woude syndrome is the most common cause of cleft lip and palate resulting from variations in a single gene, and this condition accounts for approximately 1 in 50 such cases. </s>