A patient with unilateral tibial aplasia and accessory scrotum: a pure coincidence or nonfortuitous association?

Abstract

Tibial aplasia is an uncommon lower limb malformation that can occur isolated or be part of a more complex malformation pattern. We describe a 9-year-old boy born after uneventful pregnancy and delivery. Family history was negative for maternal diabetes and other malformations. The patient presented with left tibial aplasia and homolateral prexial foot polydactyly. He also displayed enamel dysplasia and bifid scotum with cryptorchidism. Literature review failed to identify a significant syndromic association between lower limb defects of the tibial type and the genital anomalies reported here. The combination of tibial aplasia with midline genital malformations further supports the hypothesis that the tibial ray development mirrors the morphogenetic process of the radial structures. Accordingly, the malformation pattern observed in the present patient may be pathogenetically explained by an insult occurring during late blastogenesis.

Figure 1

Patient: mesomelic shortening of the left leg with internal rotation of the homolateral foot. The great toe is hypoplastic and bifid. The lateral malleous is protruding as a result from disproportionate development of the tibia and fibula.

Figure 2

Accessory scrotum originating from the normally developed scrotal sac.

Figure 3

X-ray: complete agenesis of the left tibia, shortened and thickened fibula, and hypoplastic distal femoral epiphysis.

Figure 4

The first metatarsal bone is smaller and longer as resulting from duplication of a more posterior ray. There is a rudimentary accessory metatarsal bone on the tibial side. The great toe is hypoplastic and triphalageal, while a small monophalangeal extradigit is visible on the tibial side of the first toe. The navicular and cuboid bones are unossified.