HMGCL and hyperinsulinemic hypoglycemia, familial, 4: <h4>Background</h4>To describe pregnancy complicated by deficiency of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase, an inborn error of metabolism, and kaposiform lymphangiomatosis (KLA), a lymphatic anomaly with poor prognosis.<h4>Case</h4>A 24-year-old woman with known HMG-CoA lyase deficiency and KLA presented at 6 weeks of gestation with severe vomiting and dehydration.