The isotretinoin, a 13-cis-retinoic acid, has revolutionized the management of 
severe treatment-resistant acne and it has been widely used for a range of 
dermatological conditions, in 90% of the time in young women between 13 and 45 
years of age. This agent has severe teratogenic effects, as serious 
craniofacial, cardiovascular, thymic and central nervous system malformations. 
The baseline population risk of malformations is 3-5%, but it increases to 
almost 30% in women exposed to isotretinoin during the first trimester of 
pregnancy. Generally, patients in treatment with isotretinoin avoid eventual 
pregnancy during assumption and, after its stopping, fertility and foetal 
development are normal once circulating isotretinoin levels return to normal. 
There are no known deleterious effects on male fertility and on long-term 
teratogenic effect of isotretinoin. In this report, we suppose the possibility 
to develop a foetal malformations after a long-term wash out from isotretinoin 
therapy. A 32 year-old healthy nullipara pregnant woman, with an uneventful past 
gynaecological history, was admitted in Hospital, with a severe depressive 
syndrome in a 18 weeks malformed pregnancy for thoraco-omphalopagus conjoined 
twins. She only assumed isotretinoin, at dose of 1 mg/kg a day, for a severe and 
scarring acne for 7 months. After 3 months of pharmacological wash out, patient 
become pregnant and manifested this severe malformation. Woman interrupted 
gestation, by labour induction.