Rare disease enzyme replacement therapy (Fabry/Gaucher) cost calculator

What is enzyme replacement therapy (ERT) for rare diseases?

Enzyme replacement therapy (ERT) treats inherited disorders in which a specific enzyme is missing by infusing that enzyme intravenously on a regular schedule.
Fabry disease and Gaucher disease are lysosomal storage disorders in which a deficient lysosomal enzyme lets metabolic substrates build up in cells; ERT is the standard of care for both.

The challenge is cost: ERT is among the most expensive drug therapy in the world, often KRW 100–500 million (roughly USD 75,000–380,000) per patient per year.
This calculator estimates the weight-based enzyme dose, the vial-billed drug cost, and the real annual out-of-pocket burden after Korea’s rare-disease copay special case (10%), the out-of-pocket ceiling, the rare-disease medical-cost support program, and the medical-expense tax credit, on a 2026 basis.

Korea-based estimate. This calculator is built on Korean National Health Insurance rules for 2026 (rare-disease special-copay registration, the out-of-pocket ceiling, and the KDCA rare-disease medical-cost support program). It is an educational estimate, not medical advice, and does not replace a diagnosis, a hospital quote, or an insurer/benefit decision.

ERT drugs for Fabry and Gaucher disease

Fabry disease (α-galactosidase A deficiency)

Fabry disease is an X-linked disorder in which a GLA gene defect leaves α-galactosidase A deficient, so globotriaosylceramide (GL-3) accumulates and damages the kidney, heart, and nerves.

• Agalsidase beta (Fabrazyme): 1.0 mg/kg every 2 weeks IV, 35 mg vial
• Agalsidase alfa (Replagal): 0.2 mg/kg every 2 weeks IV, 3.5 mg vial
• Migalastat (Galafold): oral chaperone, only for amenable GLA mutations (a different mechanism, not ERT)

Gaucher disease (glucocerebrosidase deficiency)

Gaucher disease is caused by a GBA gene defect that leaves glucocerebrosidase deficient, so lipid accumulates in the spleen, liver, and bone marrow, causing anemia, low platelets, hepatosplenomegaly, and bone disease.

• Imiglucerase (Cerezyme): 60 U/kg every 2 weeks IV, 400 U vial (maintenance 15–60 U/kg)
• Velaglucerase alfa (VPRIV): 60 U/kg every 2 weeks IV, 400 U vial
• Eliglustat (Cerdelga): oral substrate reduction therapy, requires CYP2D6 genotyping (a different mechanism, not ERT)

💡 In Fabry disease the per-kg dose differs 5-fold between agalsidase beta (1.0 mg/kg) and alfa (0.2 mg/kg), so the drug must be chosen by ingredient.
Gaucher enzymes are dosed in units (U) rather than milligrams (mg).

How the cost is calculated

1. Weight-based dose and vial rounding

The enzyme dose scales with body weight, but the drug is billed only in whole vials, so you round the vial count up (ceil) to cover the prescribed dose.

dose per infusion = weight(kg) × dose factor (mg/kg or U/kg)
vials = ceil(dose ÷ vial size)
drug cost per infusion = vials × price per vial

For example, agalsidase beta (35 mg vial) at 1.0 mg/kg for a 62 kg patient needs 62 mg, but rounding up buys 2 vials (70 mg), wasting 8 mg.
That vial wastage is still billed and is included in the drug cost.

2. Every-2-week dosing → annual cost

Fabry and Gaucher ERT are standardly infused every 2 weeks, i.e. 26 infusions per year (13 if given every 4 weeks).
The annual drug cost is the per-infusion cost times the number of infusions, plus a covered IV-administration fee.

3. Korean insurance list prices (reference)

Default per-vial prices follow the Korean reimbursement ceiling price (2026 basis, adjustable):

• Fabagal (same ingredient as Fabrazyme) 35 mg: about KRW 3,993,288/vial
• Replagal 3.5 mg: about KRW 2,247,476/vial
• Abcertin / VPRIV 400 U: about KRW 1,888,000/vial

Actual billed prices may differ under negotiated or risk-sharing contracts, so adjust the unit price to the value confirmed by your hospital or pharmacy.

The three safety nets that cut your cost

① Rare-disease special copay (10% coinsurance)

Fabry and Gaucher disease are registered rare-disease special-case conditions (diagnosis code E75.2, special mark V117).
Once registered, the patient pays only 10% of covered charges (versus 30% outpatient without registration).

Basis: National Health Insurance Act Art. 44 and Enforcement Decree Art. 19(1) Table 2, and the Ministry of Health and Welfare Notice on Copayment Special Cases (No. 2026-101), Art. 5 and Table 4.
Registration lasts 5 years and can be renewed while the disease persists.

② Out-of-pocket ceiling (annual cap, retroactive refund)

When annual covered out-of-pocket exceeds the income-decile ceiling, the excess is refunded.
Even at the 10% special-case rate, ERT out-of-pocket runs into the millions, so the ceiling is the key mechanism that pulls the real burden down to the income-decile cap.

For 2026 the income-decile annual ceiling ranges from about KRW 900,000 (decile 1) to KRW 8,430,000 (decile 10). These are the 2025 confirmed figures (KRW 890,000–8,260,000) adjusted for inflation; the final 2026 cap is published the following year.
It applies as prospective capping at a single provider and as a next-year refund when totals across providers exceed the personal cap.

③ Rare-disease medical-cost support (four special conditions)

The KDCA rare-disease helpline runs a medical-cost support program that covers covered-care out-of-pocket for registered patients who meet income and asset tests.

Fabry and Gaucher disease — with hemophilia and mucopolysaccharidosis — are among the four special conditions with relaxed income limits (patient household under 160% of median income).
If eligible, the remaining out-of-pocket after the special-case rate (and the ceiling) can also be supported, cutting the real burden sharply.
Support is denied above the income limit, so check eligibility at helpline.kdca.go.kr.

Frequently asked questions

Q. Is ERT really hundreds of millions of won a year?

A. Yes. Fabry and Gaucher ERT are among the most expensive drugs worldwide.
For adults it runs roughly KRW 100–500 million a year depending on weight and dose, which is why the special copay, ceiling, and support program work together.

Q. Even at 10%, the burden looks huge — what do I actually pay?

A. At KRW 200 million a year, 10% is KRW 20 million, but the out-of-pocket ceiling refunds the excess, so the real burden falls to the income-decile cap (about KRW 0.9–8.4 million).
If you also qualify for medical-cost support, even that cap can be covered.

Q. Why is vial wastage counted in the cost?

A. Enzyme vials are hard to reuse once opened, so they are billed whole.
When the prescribed dose is not an exact multiple of the vial size, the leftover is still purchased and billed, so it belongs in the cost.

Q. Can I also claim the medical-expense tax credit?

A. With earned income you get a 15% credit on out-of-pocket above 3% of total salary.
For a registered rare/intractable-disease patient’s own expenses, the credit has no KRW 7 million cap.

Estimate your ERT cost now

Enter weight, drug, and coverage settings to see how far the very high drug cost actually falls after Korea’s safety nets.

This is a 2026 reference estimate; confirm actual prices, doses, and out-of-pocket with your hospital and pharmacy.

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