A Child with Three Legs or Conjoint Parasitic Twin?

Rachiphagus is a rare congenital anomaly in which conjoined twins are fused at the midline of the vertebral column region. When one twin is malformed, the condition is referred to as a parasitic twin. The term "parasitic twin" also encompasses cases involving extra limbs or limb-like structures. Despite ongoing research, the underlying causes of this condition remain unknown.

This is a systematic review of the literature with a case report. A literature search was done in English language in PubMed and Semantic-Scholar from 1952 to 2023. All articles and cases with excess leg or mass which were attached at the back of the spine were reviewed and analysed.

A total of 65 cases with rachipagus anomaly were included in this study. Females 37 (56.9%) were affected more than males 28 (43.1%). The lower limbs were in 41 (63.1%) cases, followed by rudimental limbs and mass were in 15 (23.1%) cases, upper limbs were in 8 (12.3%) cases and rudimental upper and low limbs were in 1 (1.5%) case. In majority of cases, accessory limb or mass were attached at lumbosacral region, 27 (41.5%), followed by 12 (18.5%) cases at lumbar region, 7 (10.8%) were at thoracolumbar region, 5 (7.7%) were at sacral and other regions. More than half of the cases 34 (52%) were in Asian countries, followed by 24 (37%) cases in Africa.

Rachipagus parasitic twin is congenital abnormalities that develops during embryogenesis and exists at birth with structural deformities of the spine and additional limb or limb like mass. This article presents a novel rachipagus case and systematically reviews the relevant literature.