Parkes-Weber syndrome is a rare vascular malformation syndrome with extensive capillary malformations that appear at birth or during early childhood. Associated high-flow arteriovenous fistulas cause abnormal growth of the soft tissue and bony structures of a limb, with subsequent overgrowth of length and girth. A single lower extremity is typically involved, though cases with multiple limb involvement have been reported. High-flow arteriovenous shunts may also result in tachycardia, hypertension, and high-output cardiac failure. Cases are usually sporadic. Some cases are inherited in an autosomal dominant pattern due to mutations in the RASA1 gene. There is no known sex or ethnic predilection. Prognosis may be poor due to complications including bleeding, limb ischemia, and heart failure.