Congenital Cutaneous Hamartomas With Skeletal Muscle Differentiation Associated With LUMBAR Syndrome

Background/Objectives: Congenital skin anomalies have been observed in LUMBAR syndrome, but their clinicopathologic significance remains unclear. This study aimed to investigate the congenital, nonvascular skin anomalies in LUMBAR syndrome (lower body infantile hemangiomas, urogenital anomalies and hemangioma ulceration, spinal cord malformations, bony deformities, anorectal/arterial anomalies, and renal anomalies). We hypothesized that an association exists between complex skin hamartomas and LUMBAR syndrome, similar to recent findings in PHACE syndrome (posterior fossa anomalies, hemangioma, cerebrovascular arterial anomalies, cardiovascular anomalies, and eye anomalies). Methods: This IRB-exempt, retrospective study utilized a database of 144 published LUMBAR cases, used to establish diagnostic criteria for the syndrome, to identify individuals with nonhemangioma skin anomalies. Data extracted from identified patients included lesion location and clinical description, lesional histopathology (when available), location of the segmental infantile hemangioma, and the presence of additional congenital anomalies. Results: We discovered 57 individuals with LUMBAR syndrome and nonhemangioma skin anomalies. Of these, 5/57 (9%) presented with lumbosacral or pelvic soft tissue appendages accompanied by histopathological findings. All five exhibited complex skin hamartomas with skeletal muscle differentiation, including four with histopathologic features diagnostic or suggestive of rhabdomyomatous mesenchymal hamartoma and one with a fetal rhabdomyoma. Conclusions: This study reveals a novel association between complex skin hamartomas with skeletal muscle differentiation and LUMBAR syndrome. Our findings suggest that these complex skin hamartomas represent another common link between LUMBAR and PHACE syndromes. Furthermore, this association supports the potential role of abnormal mesodermal tissue migration during early embryogenesis in the shared pathogenesis of these syndromes.