Penoscrotal transposition was first reported by Appleby in 1923 [2]. Mcllvoy and Harris in 1955 reported the first performed surgery to move the penis into a more cranial position through a subcutaneous tunnel beneath the prepenile scrotum [3].

Scrotal engulfment, shawl scrotum, prepenile scrotum, daughter scrotum.

There is no figure about the exact incidence of PST; complete cases are stated usually as a case report, but I believe minor cases are underestimated. In our group of 11,450 child examined during routine circumcision an 82 cases of different grades of PSP anomalies diagnosed with an incidence of (0.7 %), this high incidence this group of patients attributed to special characters of the sample rolled as most of them are referred patients with a high possibility to have a different genitourinary anomalies [1]. The office of Rare Diseases (ORD) of the National Institutes of Health (NIH) estimated penoscrotal transposition, or its subtype to affect less than 200,000 people in the US population.

One aspect of sexual differentiation that still poorly understood is the mechanism controlling the position of genitalia, as the external position of male gonads represents one of the most important differences between both sexes. Embryological origin of the penis and scrotum are respectively the genital tubercle and labioscrotal folds, and at the end of the sixth week of development, males and females have indistinguishable external genitalia, then penis and scrotum achieve their usual arrangement when, under the influence of androgens, the genital tubercle elongates to become the penis and the labioscrotal folds migrate to a caudal and dorsal position to the penis, where they fuse in the midline and merge beneath the penis, the line of fusion remains as the scrotal raphe. It has been suggested that scrotal anomalies like penoscrotal transposition may result from early division and/or abnormal migration of the labioscrotal swelling [4] (Fig. 15.1).

Although most reported cases are sporadic, some suggest a genetic basis for abnormal penoscrotal relationship. Abnormal positioning of the genital tubercle in relation to the scrotal swellings during the critical fourth to fifth week of gestation may affect the inferomedial migration and fusion of the scrotal swellings. If the phallic tubercle also is intrinsically abnormal, development of the corporal bodies and the urethral groove and folds may be affected; this explains the frequent occurrence of the other genital abnormalities [5]. Lamm and Kaplan [4] suggested that unilateral failure or abnormal migration might result in unilateral penoscrotal transposition or ectopic scrotum, and early division of a labioscrotal swelling with subsequent abnormal migration might result in an accessory scrotum. Takayasu et al. [6] proposed that a teratoid growth of the divided pleuripotential anlage of he labioscrotal swelling is responsible for the accessory scrotum. Perineal lipomas have been described also as an associated condition; however, they are very commonly associated with the accessory scrotum in up to 83 % of cases, also Sule et al. [7] hypothesized that the accessory labioscrotal fold develops due to presence of perineal lipoma in the perineum which disrupts the continuity of the developing caudal labioscrotal swelling.

There is evidence that 5-alpha-reductase type 2 deficiency may be involved in PST. 5-alpha reductase type 2 deficiency is an autosomal recessive sex-limited condition that prevents the conversion of testosterone to dihydrotestosterone [8].

In marsupial animals like Kangaroo the scrotum is normally lies caudal to the penis, where in rabbits the scrotum lies partially around the phallus, so this issue deserve a more researches to elucidate the exact pathogenesis of PSP anomalies (Fig. 15.2).

PSP anomalies reported with different grades of caudal regression syndrome [9], many syndromes such as Aarskog-Scott syndrome (faciodigitogenital syndrome), Rubenstein-Taybi syndrome, craniofrontonasal dysplasia, Hunter Carpenter McDonald Syndrome, Naguib Syndrome, Saito Kuba Tsuruta Syndrome, Ieshima Koeda Inagaki syndrome, Willems de Vries syndrome, Schinzel syndrome and Seaver Cassidy syndrome. Different grades of PSP anomalies are a common feature of Popliteal pterygium syndrome.