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What Are the Most Common Rare Diseases and How Are They Treated?
What Are the Most Common Rare Diseases and How Are They Treated?
"Rare disease” sounds uncommon, but collectively these conditions affect millions of people worldwide. Globally, more than 6,000–7,000 rare diseases have been identified, many of them genetic and lifelong. While each individual disease affects a small number of people, together they represent a major public health challenge.
In this article, we look at some of the most commonly known rare diseases and how they are treated, focusing on FDA/EMA-approved medicines. We also highlight Wilson’s disease and the role of Triokris (Trientine 250 mg capsules) as part of long-term copper chelation therapy.
What Is a Rare Disease?
Definitions vary by region, but in general:
- In India, a disease is considered rare if it affects fewer than 1 in 10,000 people.
- In the EU, a disease is rare if it affects fewer than 1 in 2,000 people.
- In the U.S., it is defined as affecting fewer than 200,000 people nationwide.
Examples of better-known rare diseases include cystic fibrosis, spinal muscular atrophy (SMA), Gaucher disease, hemophilia, thalassemia, sickle cell disease, Wilson’s disease, and others.
Because many rare diseases are genetic and chronic, treatment often focuses on slowing disease progression, preventing complications, and improving quality of life rather than a complete cure.
Cystic Fibrosis (CF):
What it is:
Cystic fibrosis is a genetic disorder caused by mutations in the CFTR gene, leading to thick, sticky mucus in the lungs, pancreas, and other organs. It can cause chronic lung infections, digestive problems, and reduced life expectancy.
Key FDA/EMA-approved treatments:
- CFTR modulators (treat underlying protein defect, mutation-specific):
- Ivacaftor (Kalydeco®) – potentiator for specific gating mutations
- Lumacaftor/ivacaftor (Orkambi®) – combination for F508del homozygous mutation
- Tezacaftor/ivacaftor (Symdeko®/Symkevi®)
- Elexacaftor/tezacaftor/ivacaftor (Trikafta®/Kaftrio®) – “triple therapy” for patients with at least one F508del mutation
- Alyftrek™ (vanzacaftor/tezacaftor/deutivacaftor) – a newer once-daily triple combo approved by the FDA in 2024 for eligible CFTR mutations
Supportive/symptomatic care
- Inhaled antibiotics, bronchodilators, and mucolytics
- Pancreatic enzyme replacement
- Nutritional support and physiotherapy
These therapies have transformed outcomes, significantly improving lung function and survival in many people with CF.
Spinal Muscular Atrophy (SMA)
What it is:
SMA is a genetic neuromuscular disorder caused by a deficiency of the SMN protein due to SMN1 gene mutations. It leads to progressive muscle weakness and is a leading genetic cause of infant mortality.
Key FDA-approved disease-modifying therapies:
- Nusinersen (Spinraza®) – an intrathecal antisense oligonucleotide that modifies SMN2 splicing to increase SMN protein production.
- Onasemnogene abeparvovec (Zolgensma® / OAV101) – a one-time gene replacement therapy delivering a functional SMN1 gene via AAV9 vector; initially for patients <2 years, now expanded with intrathecal route (Itvisma™) for older children in some markets.
- Risdiplam (Evrysdi®) – an oral SMN2 splicing modifier for children and adults, offering systemic exposure and at-home administration.
These treatments have significantly improved survival and motor function, especially when started early.
Gaucher Disease
What it is:
Gaucher disease is a lysosomal storage disorder caused by a deficiency of the enzyme glucocerebrosidase, leading to the accumulation of glucocerebroside in the spleen, liver, bone marrow, and bones.
Key FDA/EMA-approved treatments:
- Enzyme Replacement Therapy (ERT) – considered the gold standard for many patients:
- Imiglucerase (Cerezyme®)
- Velaglucerase alfa (VPRIV®)
- Taliglucerase alfa (Elelyso®)
Substrate Reduction Therapy (SRT) – for some adults:
- Eliglustat (Cerdelga®)
- Miglustat (Zavesca®)
ERT can reduce organ enlargement, improve blood counts, and relieve bone symptoms. Treatment choice depends on disease type, severity, age, and regulatory approvals in each country.
Thalassemia and Sickle Cell Disease
What they are:
- Thalassemia involves inherited defects in hemoglobin chain production.
- Sickle cell disease (SCD) involves abnormal hemoglobin S, leading to sickling of red blood cells, vaso-occlusive crises, anemia, and organ damage. Both are recognized as rare diseases in many geographies, though highly prevalent in certain populations.
Key treatment approaches include:
- Regular blood transfusions for severe forms
- Iron chelation therapy (e.g., deferoxamine, deferasirox, deferiprone) to prevent iron overload
- Hydroxyurea to reduce crises in SCD
- Allogeneic stem cell transplantation for selected patients
Recently, gene therapy and gene-editing approaches have been approved in some regions for SCD and transfusion-dependent β-thalassemia, offering potential functional cure in carefully selected patients, but access remains limited and highly specialized.
Wilson’s Disease
What it is:
Wilson’s disease is a rare, autosomal recessive disorder of copper metabolism, caused by mutations in the ATP7B gene. Copper accumulates in the liver, brain, and other organs, leading to hepatic, neurological, and psychiatric symptoms if untreated.
Treatment goal:
Lifelong control of copper levels through chelating agents and/or zinc therapy to prevent accumulation and organ damage.
Main FDA/EMA-recognized therapies
D-penicillamine
- A chelating agent that binds copper and enhances urinary excretion.
- Considered a first-line decoppering agent, but it can cause significant adverse effects in some patients
Triokris (Trientine hydrochloride)
- A copper chelator used especially in patients who cannot tolerate D-penicillamine or require long-term maintenance therapy.
- FDA-approved products include trientine hydrochloride (Triokris®) for certain adult patients with stable Wilson’s disease.
Triokris™ (Trientine Hydrochloride Capsules USP 250 mg) is an example of a trientine formulation manufactured in a USFDA-approved facility and supplied from India for Wilson’s disease management in appropriate settings, under specialist supervision and in line with local regulations.
Zinc salts (e.g., zinc acetate)
Reduce intestinal copper absorption and are widely used in maintenance therapy and sometimes in presymptomatic patients.
Treatment is individualized based on disease stage, organ involvement, tolerability, and monitoring of copper status.
Why Early Diagnosis and Access to Treatment Matter:
Across all these conditions, early recognition and timely access to approved therapies can:
- Slow or prevent irreversible organ damage
- Improve survival and functional outcomes
- Reduce hospitalizations and long-term complications
- Enhance the quality of life for patients and families
Because many rare diseases require lifelong therapy, reliable supply chains and adherence to stringent quality and regulatory standards are essential—particularly when medicines are sourced or exported across borders.
How many rare diseases exist worldwide?
Estimates suggest there are over 6,000–7,000 rare diseases, with new conditions still being characterized. While each is individually rare, together they affect hundreds of millions of people globally.
Are rare diseases always genetic?
Most rare diseases are genetic and often present in childhood, but some are acquired (e.g., rare cancers, autoimmune conditions, or infections). Many rare genetic diseases are chronic and require specialized, long-term care.
Can rare diseases be cured?
Some rare diseases can be functionally cured with interventions such as stem cell transplantation or gene therapy, but many currently rely on chronic treatment to manage symptoms and prevent complications. Research in gene therapy, RNA-based drugs, and targeted biologics is rapidly evolving.
Is Wilson’s disease treatable?
Yes. Wilson’s disease is considered highly treatable when diagnosed early. Lifelong copper-chelating therapy (e.g., penicillamine or trientine) and/or zinc can control copper levels, stabilize organ function, and allow many patients to lead productive lives. However, treatment must be closely supervised by specialists.
What is Trientine (Triokris 250 mg) used for?
Trientine is a copper-chelating medicine used in the treatment of Wilson’s disease, particularly in patients who are intolerant to D-penicillamine or require long-term maintenance therapy. Trientine 250 mg capsules (such as Triokris™) help bind excess copper so it can be excreted, supporting long-term disease control under medical supervision.
Why are CFTR modulators important in cystic fibrosis?
CFTR modulators such as ivacaftor, lumacaftor/ivacaftor, tezacaftor/ivacaftor, and elexacaftor/tezacaftor/ivacaftor act on the faulty CFTR protein and address the underlying cause of cystic fibrosis in patients with eligible mutations, significantly improving lung function and survival.
How have treatments for spinal muscular atrophy changed outcomes?
Before disease-modifying therapies, SMA often led to severe disability or early death. Now, drugs like nusinersen, risdiplam, and gene therapy with onasemnogene abeparvovec have dramatically improved motor function and survival, especially when started early—highlighting the importance of newborn screening.
Key References:
Medical disclaimer: The information above is for awareness and education only. Diagnosis and treatment decisions must always be made by qualified healthcare professionals.