Background: Diphallia and penoscrotal transposition are rare, generally sporadic, abnormalities.
Case reports: Case 1: A 2-1/2-month-old boy was admitted in hospital because he suffered from complete penoscrotal transposition, with moderate hypospadias for which he was operated on. Examination at the age of 6 years showed hypoplastic and dislocated patellae. Case 2: A 2-month-old boy, brother of case 1, also suffered from incomplete penoscrotal transposition, associated with diphallia but without double bladder, that was operated on. Ultrasonography at the age of 17 months showed absence of patellae. The sister of these two patients was normal but her mother displayed ambiguous genitalia with phallic structure located beneath partially fused labial folds. Her patellae were also absent.
Conclusion: This is the first familial case of true diphallia associated to penoscrotal transposition. This abnormality is also associated to absence of patellae and seems to be dominantly inherited.