We report on a child who died in the neonatal period. Major external anomalies included foetal overgrowth, macroglossia, and ambiguous genitalia (micropenis and perineoscrotal hypospadias with cryptorchidism). Necropsy showed a large right diaphragmatic hernia, visceromegaly, multicystic kidney dysplasia, Langerhans islet hyperplasia, nephroblastomatosis, multiple adrenal adenomas, and dysplastic testicles. The child illustrates the difficulties of the differential diagnosis of overgrowth syndromes in the neonatal period, and the phenotypic overlap of Beckwith-Wiedemann, Denys-Drash, Simpson-Golabi-Behmel, Perlman and possibly Meacham-Winn syndromes. Simpson-Golabi-Behmel syndrome was felt to be the most likely diagnosis. If this opinion is correct, genital ambiguity, hydramnios and nephroblastomatosis should be added to the clinical spectrum of Simpson-Golabi-Behmel syndrome. Differential diagnosis between the above-mentioned syndromes is of major importance for accurate genetic counseling, considering the differences in recurrence risk. The present case underlines the need for long-term survey of patients suspected of having Simpson-Golabi-Behmel syndrome, who could be at risk for embryonic tumours.