G47.421

Billable

Narcolepsy in conditions classified elsewhere with cataplexy

HCC Category Mapping

RxHCCHCC 355 — Narcolepsy

0.000

What This Code Means

Narcolepsy with muscle weakness episodes that occurs as a symptom of another underlying medical condition or disease.

Coding Tips

•Requires dual coding - code the underlying condition first, then this code
•Use when narcolepsy is secondary to another classified condition (e.g., Niemann-Pick disease type C)

Clinical Significance

Narcolepsy with cataplexy secondary to another medical condition represents symptomatic narcolepsy caused by an identified underlying disorder such as sarcoidosis, multiple sclerosis, tumor, or traumatic brain injury affecting the hypothalamus. This distinction from primary narcolepsy is critical because treating the underlying condition may improve narcolepsy symptoms. The underlying condition must be coded first, making accurate sequencing essential for both clinical care and risk adjustment.

Documentation Requirements

✓Underlying causative condition identified and documented (e.g., brain tumor, sarcoidosis, multiple sclerosis, traumatic brain injury)
✓The underlying condition code must be sequenced FIRST per ICD-10-CM convention
✓Narcolepsy symptoms documented: excessive daytime sleepiness
✓Cataplexy episodes documented with emotional triggers
✓Temporal relationship between underlying condition and narcolepsy onset
✓Sleep study results supporting narcolepsy diagnosis
✓Treatment plan addressing both underlying condition and narcolepsy symptoms

Commonly Confused Codes

G47.411 (Narcolepsy with cataplexy, primary) — use when narcolepsy is idiopathic, not secondary to another condition G47.429 (Narcolepsy in conditions classified elsewhere, without cataplexy) — secondary narcolepsy but lacks cataplexy G47.14 (Hypersomnia due to a medical condition) — excessive sleepiness from medical condition without full narcolepsy criteria G93.1 (Anoxic brain damage) — may cause secondary narcolepsy but is the underlying condition, not the narcolepsy itself G47.419 (Narcolepsy without cataplexy, primary) — primary form without cataplexy

Code Hierarchy

└G47Sleep disorders └G47.4Narcolepsy and cataplexy └G47.42Narcolepsy in conditions classified elsewhere └G47.421Narcolepsy in conditions classified elsewhere with cataplexy

└G47.421Narcolepsy in conditions classified elsewhere with cataplexy