The three cardinal features of Sotos syndrome include a characteristic facial gestalt, learning difficulties, and macrocephaly, and greater than 90% of patients are noted to have all three features (Tatton-Brown and Rahman 2004). The characteristic facial gestalt is most recognizable between the ages of one and six and consists of a long, thin face with down-slanting palpebral fissures, a broad forehead, malar flushing, and fronto-temporal hair sparsity. Learning disabilities are present in 97% of individuals with Sotos syndrome, but the extent of impairment is largely variable (Tatton-Brown et al., 2005). Approximately 90% of individuals with Sotos syndrome have height and/or head circumference at least 2 standard deviations above the mean in childhood. Other major features present in more than 15% of patients include advanced bone age, cardiac anomalies, cranial magnetic resonance imaging or CT abnormalities, hyperlaxity, maternal pre-eclampsia, neonatal hypotonia, neonatal jaundice, neonatal poor feeding, renal anomalies, scoliosis, and seizures. As with other overgrowth syndromes, there is an increased risk for tumors in Sotos syndrome. The risk is estimated to be 2-3% and includes embryonal tumors such as Wilms tumor, neuroblastoma, and hepatocellular carcinoma, as well as other benign and malignant tumors including leukemia, lymphoma, and saccrococcygeal teratoma (Lapunzina 2005). In previous studies, Sotos syndrome has demonstrated complete penetrance, as all individuals with Sotos syndrome exhibit at least some characteristics of the disorder.