A study carried out by Bausch et al. in NF 1 patients with associated pheochromocytoma showed that the cysteine-serine rich domain was affected in 35% of the cases whereas the Ras GTPase activating protein domain in only 13%, suggesting that the cysteine-serine rich could play a role in the formation of NF1-associated pheochromocytoma. The gene discussed is RASA2; the disease is pheochromocytoma.