Crystal's Coder Hub🧬 ICD-10-CM G72.3 — Periodic Paralysis
Billable Code Confirmed
ICD-10-CM G72.3 is a valid, billable 4-character diagnosis code. The first three characters (G72) specify other and unspecified myopathies, and the 4th character (3) uniquely identifies periodic paralysis. No additional characters are required.
Non-Billable Parent Codes — Never Submit These
Clinical Context: Channelopathies
Periodic paralysis is a group of rare, inherited neurological disorders (channelopathies) caused by mutations in the genes that regulate sodium, calcium, or potassium ion channels in skeletal muscle cell membranes. These defects cause the muscles to become temporarily unresponsive to nerve signals, leading to episodes of profound weakness or flaccid paralysis.
Code Classification
ICD-10-CM Diagnosis Code — wRVU, assistant payable, and global period fields are not applicable. See CPT Procedural Crosswalk and ICD-10-PCS Crosswalk sections for associated procedural billing.
🔍 Code Description
ICD-10-CM G72.3 classifies Periodic paralysis. This includes several distinct clinical variants that all share the hallmark symptom of episodic, painless muscle weakness or paralysis that can last from minutes to days.
The variants are typically classified by how they respond to or present with blood potassium levels during an attack:
- Hypokalemic periodic paralysis (HypoKPP): The most common form. Attacks are associated with a drop in blood potassium and are often triggered by carbohydrate-rich meals, rest after vigorous exercise, or stress.
- Hyperkalemic periodic paralysis (HyperKPP): Attacks are associated with elevated blood potassium. Triggers include potassium-rich foods, fasting, or exposure to cold.
- Normokalemic periodic paralysis: A rare variant where potassium levels remain normal during attacks.
- Andersen-Tawil syndrome: A rare type that also includes cardiac arrhythmias and distinctive physical features (maps here unless otherwise specified by the provider).
Unlike muscular dystrophies, the strength between attacks is completely normal in the early stages of the disease, though permanent fixed weakness can develop later in life.
🌳 Code Tree / Hierarchy
G72 Other and unspecified myopathies ❌ Non-billable
│
├── G72.0 Drug-induced myopathy ✅ Billable
├── G72.1 Alcoholic myopathy ✅ Billable
├── G72.2 Myopathy due to other toxic agents ✅ Billable
├── G72.3 Periodic paralysis ◀ THIS CODE ✅ Billable
├── G72.4- Inflammatory and immune myopathies, not elsewhere classified
├── G72.8- Other specified myopathies
└── G72.9 Myopathy, unspecified ✅ Billable
Grouping All Variants
ICD-10-CM does not have separate specific codes for Hypokalemic vs. Hyperkalemic periodic paralysis. All primary familial and genetic periodic paralyses map to G72.3. If the patient has a secondary, acquired form (e.g., thyrotoxic periodic paralysis), it requires additional coding for the underlying etiology.
✅ Includes
The following clinical terms and syndromes map directly to G72.3 when documented:
- Familial periodic paralysis
- Hyperkalemic periodic paralysis
- Hypokalemic periodic paralysis
- Myotonic periodic paralysis
- Normokalemic periodic paralysis
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with CODE
| Code | Description | Note |
|---|---|---|
| E70-E88 | Metabolic myopathies | Mutually exclusive. Conditions like Pompe disease or McArdle disease are distinct metabolic defects rather than primary ion channelopathies. |
| M60.- | Myositis | Mutually exclusive. Inflammatory muscle diseases are classified under diseases of the musculoskeletal system. |
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| E05.90 | Thyrotoxicosis, unspecified | Thyrotoxic periodic paralysis (TPP) is a known complication of hyperthyroidism. If documented, code the thyrotoxicosis first, followed by G72.3 to fully describe the etiology and manifestation. |
📋 Clinical Overview
Common Diagnoses / Clinical Indications
Patients assigned this code typically present in the ED or neurology clinics with:
- Episodic Weakness: Sudden onset of flaccid weakness, typically involving the proximal muscles of the limbs (shoulders and hips). Bulbar and respiratory muscles are usually spared but can be affected in severe attacks.
- Recognizable Triggers: A history of attacks following high-carbohydrate meals, cold exposure, or a period of rest following intense exercise.
- Family History: Often an autosomal dominant inheritance pattern.
- EMG Findings: Specialized Exercise EMG protocols will show significant drops in the Compound Muscle Action Potential (CMAP) amplitude during or after exercise.
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (2024-2025 Implementation) |
| HCC Assignment | ✅ Mapped — HCC 75 |
| HCC Category | Myasthenia Gravis, Myopathies, and Other Neurological Disorders |
| RAF Impact | Captures the complexity of managing a chronic neuromuscular condition requiring specialized prophylactic therapies (e.g., carbonic anhydrase inhibitors like acetazolamide or dichlorphenamide). |
Capture Annually
Even if a patient has been attack-free for the entire year due to successful prophylactic medication management, the condition is a permanent genetic disorder. It must be addressed, documented (MEAT criteria), and coded at least once per calendar year to maintain accurate risk adjustment profiles.
🏥 DRG Assignment
MDC 01 — Diseases and Disorders of the Nervous System
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 091 | Other Disorders of Nervous System with MCC | ~1.95 |
| DRG 092 | Other Disorders of Nervous System with CC | ~1.10 |
| DRG 093 | Other Disorders of Nervous System without CC/MCC | ~0.80 |
Approximate. Verify against IPPS FY2026 Final Rule tables.
🛠️ Commonly Associated CPT Codes (Neurology / ED / Outpatient)
Diagnostic and Management Context
Diagnosis often involves provocative EMG testing and genetic screening, while acute management in the ED relies heavily on laboratory evaluation and careful electrolyte administration.
| CPT Code | Description | Modifier Notes / wRVU |
|---|---|---|
| 99284 / 99285 | Emergency department visit (High MDM) | Frequently used when patients present during an acute paralytic attack requiring immediate workup and monitoring. |
| 95860 | Needle electromyography; one extremity with or without related paraspinal areas | Used during the diagnostic phase. (wRVU: ~1.20 for modifier 26) |
| 80051 | Electrolyte panel | Essential lab test to determine if the attack is hypokalemic or hyperkalemic. |
| 81404 / 81405 | Molecular pathology procedures (Tier 2) | Genetic testing codes used to sequence specific ion channel genes (e.g., CACNA1S, SCN4A, KCNJ2). |
💊 Coding Scenarios and Examples
Scenario 1 — Outpatient Neurology Visit (Established)
Clinical Vignette: A 28-year-old male with an established diagnosis of Hypokalemic Periodic Paralysis presents to the neurology clinic for a routine follow-up. He reports having only one minor attack of leg weakness in the past 6 months since starting dichlorphenamide (Keveyis). He brings his potassium log, which shows levels have remained stable. The neurologist refills his medication, reviews his low-carbohydrate diet, and schedules a follow-up in 6 months. Moderate MDM.
Diagnoses:
- G72.3 — Periodic paralysis (Primary reason for the visit)
Procedure:
- 99214 — E/M established patient, Moderate MDM
Scenario 2 — Emergency Department: Acute Attack
Clinical Vignette: A 19-year-old female presents to the ED with profound inability to move her arms and legs that began 2 hours after a heavy pasta dinner. She has a known history of familial periodic paralysis. Her airway is intact. Stat labs show a serum potassium of 2.1 mEq/L (severe hypokalemia). The ED physician orders IV potassium chloride with continuous cardiac monitoring. Once her potassium reaches 3.5 mEq/L, her strength completely normalizes, and she is discharged home.
Diagnoses:
- E87.6 — Hypokalemia (The acute metabolic crisis driving the symptoms)
- G72.3 — Periodic paralysis (The underlying genetic etiology/manifestation)
Procedure:
- 99285 — Emergency department visit, High MDM (Life-threatening metabolic derangement requiring continuous monitoring and IV intervention)
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Defaulting to Unspecified Weakness. Using R27.- (Lack of coordination) or M62.81 (Muscle weakness) instead of G72.3 when the patient has a confirmed diagnosis of periodic paralysis causes a severe loss of clinical specificity and misses out on critical HCC risk adjustment data. |
| ❌ | Ignoring Secondary Causes. If the periodic paralysis is explicitly documented as secondary to hyperthyroidism (Thyrotoxic periodic paralysis), failing to code the thyrotoxicosis (E05.-) leaves the primary etiology out of the clinical picture. |
| ✅ | Query for Type if Ambiguous. While all familial types map to G72.3, it is clinically vital to know if the patient is hypokalemic or hyperkalemic for treatment safety. Ensure the provider has clearly documented the patient’s specific subtype in the clinical notes. |
| ✅ | Capture Annually for Risk Adjustment. Because periodic paralysis is a permanent channelopathy that requires ongoing prophylactic therapies, it easily meets the MEAT criteria and should be coded annually to accurately reflect the patient’s HCC risk.^4 |
📚 Sources
1. CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2025/FY2026. Section I.C.6: Diseases of the Nervous System.2. Statland, J. M., et al. (2018). Review of the diagnosis and treatment of periodic paralysis. Muscle & Nerve, 57(4), 522-530. (Source for pathophysiology and clinical presentation).
3. Fontaine, B. (2008). Periodic paralysis. Advances in Genetics, 63, 3-23.
4. CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings.
5. American Medical Association (AMA). CPT Professional Edition 2025. Evaluation and Management Guidelines.