- Encephalocraniocutaneous lipomatosis (ECCL) is a congenital neurocutaneous syndrome that comprises unilateral porencephalic cysts with cortical atrophy; ipsilateral hamartomas of scalp, eyelid, and outer part of the eye; lipomas of the central nervous system (CNS); cranial asymmetry; and characteristic cutaneous lesions. We report on the antenatal and postnatal sonographic and radiologic, and on the postnatal pathologic findings of an infant diagnosed with ECCL at birth. The antenatal sonogram at 28 weeks of gestation showed normal intracranial structures; the sonogram at 38 weeks of gestation showed asymmetry of the cerebral hemispheres and ventriculomegaly. Magnetic resonance imaging at age 6 weeks demonstrated a porencephalic cyst on the left, hemiatrophy of the left cerebrum with cortical dystrophy, and a lipoma in the middle cranial fossa. Histologic findings of the resected cutaneous lesion confirmed the presence of fibrolipoma hamartoma. This case offers a unique insight into the antenatal and postnatal development of the hamartoneoplastic lesions of ECCL, and it highlights the difficulties inherent in the antenatal sonographic diagnosis of hamartoneoplastic syndromes.