A Case of Encephalocraniocutaneous Lipomatosis (ECCL) With Atypical Clinical Presentation Diagnosed on Molecular Testing: FGFR1 ECCL Tumor Risk.

Encephalocraniocutaneous lipomatosis (ECCL) is a neurocutaneous condition caused by postzygotic mosaic activating variants in genes including FGFR1, NRAS, or KRAS. It primarily affects the skin, eyes, and central nervous system. Diagnosis is typically based on characteristic clinical features and/or molecular confirmation. Here we report a unique case of ECCL in a 12-year-old female with abdominal wall lipoma, ipsilateral lower limb overgrowth, and brachydactyly, in whom somatic mosaicism for FGFR1 was identified using resected lipomatous tissue. Imaging studies confirmed additional spinal lipomas consistent with ECCL. This report expands the phenotypic spectrum of FGFR1-ECCL and underscores the importance of tissue-based somatic testing for diagnosis. Tumor risk is also discussed.