G47.421 ICD-10-CM Code: Narcolepsy in conditions classified elsewhere with cataplexy

Code

G47.421

Description

Narcolepsy in conditions classified elsewhere with cataplexy

HCC (V28)

No CMS-HCC V28 mapping

RAF reference coefficient

—

Billable

Yes

Payment year

2026

HCC Category Mapping

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work G47.421 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for G47.421

What This Code Means

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for G47.421 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

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

Child Codes