Mermaid syndrome (sirenomelia): a rare congenital malformation

Abstract

HIGHLIGHTS Sirenomelia may present with variable systemic anomalies, and not all classical abnormalities reported in the literature are necessarily observed. Comprehensive evaluation of the gastrointestinal and urogenital systems is crucial due to their high frequency of involvement in sirenomelia cases.   ABSTRACT Objective: Sirenomelia, also known as mermaid syndrome, is an exceptionally rare and severe congenital malformation characterized by partial or complete fusion of the lower limbs, often resembling a mermaid’s tail. This anomaly is frequently accompanied by multiple visceral and systemic abnormalities, particularly involving the gastrointestinal, genitourinary, and cardiovascular systems. The incidence of sirenomelia is estimated to range from 1 in 60,000 to 1 in 100,000 live births, with a generally poor prognosis due to the severity of the associated internal defects. Case Report: We report a case of a newborn presenting with sirenomelia of the symelia type, defined by complete fusion of both lower limbs into a single structure. Physical examination revealed the absence of external genitalia and an imperforate anus. Skeletal radiography confirmed the presence of both femoral and tibiofibular bones within the fused extremities. Further evaluation demonstrated severe gastrointestinal malformations, including the absence of a normal anal opening, while other anomalies commonly reported in the literature, such as renal agenesis or cardiac defects, were not identified in this patient. Conclusion: This case illustrates the wide clinical spectrum and phenotypic variability of sirenomelia. Although it is typically associated with extensive visceral involvement, not all classical anomalies are necessarily present. Comprehensive systemic evaluation is crucial for accurate diagnosis and management planning, as gastrointestinal and urogenital malformations occur frequently and significantly influence prognosis and survival outcomes.