Background

Congenital accessory limb is a rare but known anomaly [1]. The etiology described is multifactorial. But known causes might include perinatal drugs, abuse, medication, or injury. These deformities might as well occur alone or in conjunction with other anomalies [2, 3]. The authors have postulated many hypotheses mainly based on hedgehog pathway which undertakes the complex process in formation of accessory limb [3].

Polymelia is a condition in which an adjunct limb is formed in addition to the normal limbs on various locations of the body depending upon the type of genetic defect in a developing embryo [4]. When the accessory limb is present on the back, in association with the spinal cord (lumbosacral region), it is referred to as Notomelia. Polymelia is an exceedingly infrequent genetic abnormality with only a scarce number of reported cases in many years. In this case report, we present a similar literature review of a neonate who was born with a hypoplastic limb attached to her lumbosacral region.

Case presentation

A 3-day-old neonate was presented to the Children's Hospital Emergency. Her initial complaints were an extra limb arising from her lower back as seen in Fig. 1. She was born as a result of cousin marriage, after 9 months of pregnancy via spontaneous vaginal delivery and was not diagnosed antenatally. The mother was 30 years old and had two babies prior to this one who were perfectly healthy. Her weight at the time was 4.5kg (with the limb attached). We could identify the knee and foot with the toes attached. The limb was hypoplastic and had no power of its own, and the baby was unable to hold it against the gravity but she cried when it was pinched describing pain sensations. There were no genital abnormalities. Radiograph showed hemimelia, only a single-bone formation in both the limbs which could not be seen arising from the vertebral column. The patient was shifted to operation theater as seen in Fig. 2a. A circumferential incision was made (Fig. 2b), communication was dislodged (Fig. 2c), and parasitic limb excision was done (Fig. 2d).

Fig. 1
figure 1

Extra limb arising from lumbosacral region

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Fig. 2
figure 2

a Parasitic limb can be seen. b Incision made around the parasitic limb. c Dissection of the limb being done. d Parasitic limb after complete excision

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Discussion

The first-reported case of an accessory limb was in 1975, a baby born with three limbs [5], followed by literature of some with other congenital anomalies and neurological defects [6]. The basic etiology of accessory limb formation lies in problem with limb bud generation resulting in formation of parasitic limb. Due to the multiple limb presence, congenital accessory limb can be diagnosed as a remnant of a parasitic twin [7]. Limb formation and growth is a complicated process of embryonal development requiring the genetic regulation events to happen at the exact time and with the predetermined accurate genes [8]. According to a report, the alternation in a gene known as “Bovine NHLRC2” is related to the occurrence of abnormalities like Notomelia [7, 8]. This gene is the gene that is also associated with the development of polymelia. Findings in animal models have explained a great deal about these functions and have improved our understanding of malformations [8].

With the advancement in the field of technology, numerous imaging techniques are present that can detect the presence of these genetic defects even before birth and their surgical removal is made easier by assessing their development in utero. In the case of Notomelia [9], the surgical intervention can be quite complex because the accessory appendage in this instance is attached to the spinal cord, which means there is the involvement of a neurological component rather than a simple surgical leg removal process [10]. Therefore, a very careful surgery performed by adept pediatric surgeons is needed to get rid of accessory appendage.

Conclusion

Every child with parasitic limb is a surgical dilemma. Thus, a multi-disciplinary approach and a carefully planned surgery with meticulous dissection can result in complete excision of a parasitic limb without any complications.