Syndrome of Developmental Retardation, Facial and Skeletal Anomalies, and Hyperphosphatasia in Two Sisters: Nosology and Genetics of the Coffin-Siris Syndrome

We report on 2 sisters, 3 and 6 years old, with a possible new syndrome consisting of developmental retardation, facial and skeletal anomalies, and hyperphosphatasia. This disorder closely resembles the Coffin-Siris syndrome (McKusick number 135900). We describe the difficulties in achieving a diagnosis. A major diagnostic clue was the radiological recognition of hypoplasia/aplasia of the terminal phalanx of the 5th finger. Minor facial anomalies and mental retardation alone had not led to the proper diagnosis. Still, several diagnostic possibilities remain. For unknown reasons both children have an increased level of serum alkaline phosphatase activity.