Autoimmune Conditions: Symptoms, Causes & Treatment

🩺 Medically reviewed by the Health Decoded Guide Editorial Team • Last reviewed: August 2026

Autoimmune conditions develop when the immune system mistakenly attacks healthy cells, tissues or organs in the body. Different autoimmune diseases can affect the joints, skin, thyroid, digestive system, nervous system and many other parts of the body.

Health Decoded Guide provides easy-to-understand, medically reviewed information to help you understand autoimmune conditions, their symptoms, possible causes, diagnosis, treatment and how they may affect everyday life.

Symptoms can vary widely and may come and go over time. Because tiredness, joint pain, rashes and other symptoms can have many causes, having these symptoms does not necessarily mean you have an autoimmune disease.

Browse autoimmune conditions below.

🛡️ Autoimmune Disease Basics

• What Is an Autoimmune Disease?
• How the Immune System Works
• Why Does the Immune System Attack the Body?
• What Causes Autoimmune Diseases?
• Who Is More Likely to Develop an Autoimmune Disease?
• Autoimmune Disease Symptoms
• Autoimmune Disease Flare-Ups
• Can You Have More Than One Autoimmune Disease?

🦴 Joint & Connective Tissue Autoimmune Conditions

• Rheumatoid Arthritis
• Systemic Lupus Erythematosus (SLE)
• Ankylosing Spondylitis
• Psoriatic Arthritis
• Sjögren's Syndrome
• Systemic Sclerosis (Scleroderma)
• Polymyalgia Rheumatica
• Polymyositis
• Dermatomyositis

🦋 Thyroid & Hormonal Autoimmune Conditions

• Hashimoto's Thyroiditis
• Graves' Disease
• Type 1 Diabetes
• Addison's Disease

🧴 Skin & Hair Autoimmune Conditions

• Psoriasis
• Vitiligo
• Alopecia Areata
• Pemphigus
• Bullous Pemphigoid

🥣 Digestive System Autoimmune Conditions

• Coeliac Disease
• Crohn's Disease
• Ulcerative Colitis
• Autoimmune Hepatitis
• Primary Biliary Cholangitis

🧠 Brain, Nerve & Muscle Autoimmune Conditions

• Multiple Sclerosis (MS)
• Myasthenia Gravis
• Guillain-Barré Syndrome
• Autoimmune Encephalitis

🩸 Blood & Blood Vessel Autoimmune Conditions

• Autoimmune Haemolytic Anaemia
• Immune Thrombocytopenia (ITP)
• Antiphospholipid Syndrome
• Vasculitis

🔬 Diagnosis & Testing

• How Autoimmune Diseases Are Diagnosed
• ANA Test Explained
• ESR and CRP Explained
• Autoantibody Tests Explained
• Why Autoimmune Diseases Can Take Time to Diagnose
• When You May Be Referred to a Rheumatologist

💊 Treatment & Management

• Autoimmune Disease Treatment Explained
• Steroids (Corticosteroids) Explained
• Immunosuppressant Medicines Explained
• Biologic Medicines Explained
• Managing an Autoimmune Flare-Up
• Exercise and Autoimmune Conditions
• Living With an Autoimmune Disease

🚨 When to Seek Medical Care

• Persistent Unexplained Joint Pain or Swelling
• Recurrent or Unexplained Rashes
• Persistent Unexplained Fatigue
• New Muscle Weakness
• New Numbness or Neurological Symptoms
• Symptoms Affecting Several Parts of the Body
• When Autoimmune Symptoms Need Urgent Medical Attention