vised study design and manuscript preparation. PS conducted statistical analyses and wrote the first draft of the manuscript. All authors had full access to all data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Conflict of interest:
=====================

All authors report they have no conflicts of interest. Dr. Potenza has received financial support or compensation for the following: Dr. Potenza has consulted for and advised Lundbeck and Ironwood; has received research support from the National Center for Responsible Gaming and Mohegan Sun Casino; has participated in surveys, mailings or telephone consultations related to drug addiction, impulse control disorders or other health topics; has consulted for gambling entities and law offices on issues related to impulse control disorders; provides clinical care in the Connecticut Department of Mental Health and Addiction Services Problem Gambling Services Program; has guest-edited journal sections; has given academic lectures in grand rounds, CME events and other clinical or scientific venues; and has generated books or book chapters for publishers of mental health texts.


CASE PRESENTATION {#s1}
=================

Patient 1 is a 16-yr-old Caucasian female born at term after an uncomplicated pregnancy. Her 15-yr-old sister was born at 36 weeks' gestation by emergency cesarean section due to fetal distress. Both sisters have severe intellectual disability, no language, autistic features, hypotonia, and a thin habitus. They share distinctive craniofacial features including a broad/prominent forehead, hypertelorism, downslanting palpebral fissures, prominent nasal root, thick eyebrows, hirsutism, cleft chin, and strikingly prominent upper central incisors ([Table 1](#MCS002410KOBTB1){ref-type="table"}). They have a history of feeding difficulties, seizures, and developmental delay. The parents were unaffected, and there was no relevant family history.

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Clinical features of proband (16-yr-old femal