As of October 2015, ICD-9 codes are no longer used for medical coding. Instead, use this equivalent ICD-10-CM code, which is an exact match to ICD-9 code 327.42:
Billable codes are sufficient justification for admission to an acute care hospital when used a principal diagnosis.
327.42 is a legacy non-billable code used to specify a medical diagnosis of rem sleep behavior disorder. This code was replaced on September 30, 2015 by its ICD-10 equivalent.
References found for the code 327.42 in the Index of Diseases and Injuries:
Is it hard for you to fall asleep or stay asleep through the night? Do you wake up feeling tired or feel very sleepy during the day, even if you have had enough sleep? You might have a sleep disorder. The most common kinds are
General Equivalence Map Definitions The ICD-9 and ICD-10 GEMs are used to facilitate linking between the diagnosis codes in ICD-9-CM and the new ICD-10-CM code set. The GEMs are the raw material from which providers, health information vendors and payers can derive specific applied mappings to meet their needs.