Andersen syndrome (AS) is a rare disease characterized by the presence of 
periodic paralysis (PP), cardiac arrhythmia and dysmorphic abnormalities. We 
report herein the first Brazilian patient presenting AS who also had obesity, 
obstructive sleep apnea (OSA) and daytime sleepiness. Clinical and genetic 
evaluation of six family members demonstrated that four had dysmorphic 
abnormalities but none had PP or cardiac arrhythmia. Sequencing of KCNJ2 
revealed the R218W mutation in the index patient and her 6-year-old daughter, 
who presented dysmorphic abnormalities (micrognathia, clinodactyly of fourth and 
fifth fingers, short stature) and OSA. Three relatives had clinodactyly as the 
only manifestation but the R218W mutation was absent, suggesting that this 
characteristic may be influenced by another gene. OSA accompanied by dysmorphic 
features may be related to AS.