73 Diseases That Start With The Letter I

Have you ever wondered about diseases that start with the letter “I”? Wonder no more, this article is exactly what you are looking for.

In this article, I will dive into the realm of some known and lesser-known diseases beginning with this enigmatic letter I, aiming to raise awareness and understanding.

So, without any further ado, let’s embark on this fascinating journey and broaden our understanding of diseases that start with the letter I.


Diseases That Start With I

The followings are some known and lesser-known diseases that begin with the letter I (In alphabetical order):

1. Ichthyosis: Ichthyosis refers to a group of genetic skin disorders characterized by dry, scaly, and thickened skin. These conditions result from a deficiency of proteins that play a crucial role in maintaining skin moisture, leading to a buildup of dead skin cells. While there is no cure, treatment involves managing symptoms with moisturizers and topical creams.

2. Idiopathic Epilepsy: Idiopathic epilepsy is a neurological disorder characterized by recurrent seizures with no apparent cause. It is the most common form of epilepsy, and while the exact cause remains unknown, seizures can often be managed with antiepileptic medications.

3. Idiopathic Hypersomnia: Idiopathic hypersomnia is a sleep disorder characterized by excessive daytime sleepiness, despite getting adequate sleep at night. Individuals with this condition may struggle to stay awake during the day and may experience difficulty in performing daily tasks.

4. Idiopathic Hypoparathyroidism: Idiopathic hypoparathyroidism is a rare disorder where the parathyroid glands fail to produce enough parathyroid hormone, leading to low calcium levels in the blood. This can result in symptoms such as muscle cramps, tingling sensations, and seizures.

5. Idiopathic Neuropathy: Idiopathic neuropathy is a term used to describe nerve damage or dysfunction of unknown cause. It can lead to various symptoms, such as tingling, numbness, and weakness in the affected areas.

6. Idiopathic Parkinson’s Disease: Parkinson’s disease is a progressive neurological disorder that affects movement, causing tremors, stiffness, and balance problems. When the cause of Parkinson’s disease is unknown, it is referred to as idiopathic Parkinson’s disease.

7. Idiopathic Pulmonary Fibrosis (IPF): IPF is a chronic and progressive lung disease where the lung tissues become scarred and thickened, leading to breathing difficulties and reduced lung function. The exact cause of IPF is unknown, and treatment often focuses on managing symptoms and slowing disease progression.

8. Idiopathic Pulmonary Hypertension: Idiopathic pulmonary hypertension is a rare and serious condition where there is high blood pressure in the arteries that supply the lungs. This can strain the heart and lead to various symptoms, such as shortness of breath and fatigue.

9. Idiopathic Scoliosis: Scoliosis is a condition characterized by an abnormal curvature of the spine. When the cause of scoliosis is not identifiable, it is referred to as idiopathic scoliosis. Treatment options depend on the severity of the curvature and may include observation, bracing, or surgery in severe cases.

10. Idiopathic Thrombocytopenic Purpura (ITP): ITP is an autoimmune disorder where the immune system mistakenly attacks and destroys platelets, leading to a low platelet count. This can result in easy bruising and bleeding, and in some cases, treatment may involve medications or procedures to increase platelet count.

11. Ileus: Ileus is a condition where there is a temporary blockage of the intestines, leading to a disruption in the normal flow of food and fluids. It can cause abdominal pain, bloating, and constipation. Treatment often involves rest, fluids, and addressing the underlying cause.

12. Immune Thrombocytopenia: Immune thrombocytopenia is a disorder similar to ITP, where the immune system attacks platelets, leading to a low platelet count. It can increase the risk of bleeding and may require treatment to raise platelet levels.

13. Immunodeficiency: Immunodeficiency refers to a weakened or compromised immune system, making individuals more susceptible to infections. It can be inherited or acquired and may require medical management to prevent and treat infections.

14. Impaired Glucose Tolerance (IGT): IGT is a condition where blood sugar levels are higher than normal but not high enough to be classified as diabetes. It is considered a prediabetic condition and may increase the risk of developing type 2 diabetes in the future.

15. Impaired Renal Function: Impaired renal function refers to reduced kidney function, which can be caused by various medical conditions. It can lead to kidney damage and may require management through lifestyle changes and medical interventions.

16. Impetigo: Impetigo is a highly contagious skin infection caused by bacteria, primarily affecting young children. It results in red sores that rupture, ooze, and form a characteristic golden crust. Antibiotics are often used to treat impetigo.

17. Impotence (Erectile Dysfunction): Impotence, also known as erectile dysfunction (ED), is a condition where a man has difficulty achieving or maintaining an erection sufficient for sexual intercourse. It can be caused by various factors, including underlying health conditions, stress, and lifestyle choices. Treatment options may include medications, therapy, or lifestyle changes.

18. Inclusion Body Myositis: Inclusion body myositis (IBM) is a rare and progressive muscle disorder that primarily affects older adults. It leads to muscle weakness and wasting, particularly in the arms and legs. While the exact cause is unknown, there is currently no cure for IBM, and treatment focuses on managing symptoms and maintaining mobility.

19. Inclusion Conjunctivitis: Inclusion conjunctivitis is a type of conjunctivitis caused by the bacteria Chlamydia trachomatis. It can lead to red, irritated eyes and is often transmitted through direct contact with infected genital secretions during childbirth or sexual activity.

20. Indigestion: Indigestion, also known as dyspepsia, refers to a group of symptoms affecting the upper abdomen, including bloating, discomfort, and early satiety. It can be caused by various factors, such as overeating, consuming fatty or spicy foods, and stress.

21. Infantile Colic: Infantile colic is a common condition in newborns, characterized by excessive crying and fussiness for extended periods, often in the late afternoon or evening. The exact cause is unknown, but it typically improves on its own as the baby grows.

22. Infantile Hemangioma: Infantile hemangioma is a benign growth of blood vessels that commonly occurs in infants. It appears as a red or purple birthmark on the skin and often resolves on its own without treatment.

23. Infantile Pompe Disease: Infantile Pompe disease is a rare genetic disorder where the body lacks an enzyme needed to break down glycogen, leading to its accumulation in various organs, particularly the muscles and heart. It can cause muscle weakness and respiratory problems and requires early medical intervention for management.

24. Infantile Refsum Disease: Infantile Refsum disease is a rare inherited metabolic disorder where the body cannot break down certain fatty acids, leading to their accumulation in the tissues. Symptoms may include visual impairment, hearing loss, and developmental delays.

25. Infantile Spasms: Infantile spasms are a type of seizure disorder that typically occurs in infants under the age of one. They are characterized by sudden jerking movements or spasms and may indicate an underlying neurological problem.

26. Infection: Infection refers to the invasion and multiplication of harmful microorganisms, such as bacteria, viruses, or fungi, in the body. Infections can cause a wide range of symptoms, depending on the affected area, and may require appropriate treatment, such as antibiotics or antiviral medications.

27. Infectious Arthritis: Infectious arthritis, also known as septic arthritis, is a joint infection caused by bacteria or other pathogens. It can lead to joint pain, swelling, and fever and requires prompt medical treatment to prevent joint damage.

28. Infectious Mononucleosis: Infectious mononucleosis, often referred to as mono or the “kissing disease,” is a viral infection caused by the Epstein-Barr virus (EBV). It is commonly spread through saliva and can cause flu-like symptoms, sore throat, and swollen lymph nodes.

29. Infertility: Infertility is a condition where a couple is unable to conceive after one year of unprotected intercourse. It can be caused by various factors in both men and women and may require medical evaluation and assisted reproductive techniques for conception.

30. Inflammatory Bowel Disease (IBD): Inflammatory bowel disease is a group of chronic inflammatory conditions that primarily affect the gastrointestinal tract. The two main types are Crohn’s disease and ulcerative colitis. They can lead to symptoms such as abdominal pain, diarrhea, and weight loss and may require long-term medical management.

31. Influenza: Influenza, commonly known as the flu, is a viral respiratory infection that can cause fever, cough, body aches, and fatigue. It is highly contagious and spreads through respiratory droplets.

32. Influenza A: Influenza A is one of the strains of the influenza virus that can cause seasonal flu outbreaks. It is responsible for most flu-related illnesses in humans and can also infect animals.

33. Ingrown Nail: An ingrown nail occurs when the edge of the nail grows into the surrounding skin, leading to pain, swelling, and redness. Proper nail care and, in severe cases, surgical intervention can help alleviate the condition.

34. Ingrown Toenail: Similar to an ingrown nail, an ingrown toenail is a condition where the edge of the toenail grows into the surrounding skin, causing pain and inflammation.

35. Inguinal Hernia: An inguinal hernia is a condition where a part of the intestine or abdominal tissue protrudes through a weak spot in the abdominal wall near the groin area. Surgery is usually required to repair the hernia and prevent complications.

36. Inherited Heart Conditions: Inherited heart conditions refer to a group of heart disorders that are passed down through families due to genetic mutations. These conditions can affect the heart’s structure and function and may require lifelong monitoring and management.

37. Insect Bites: Insect bites are common skin reactions to bites or stings from various insects. They can cause redness, itching, and swelling and may require topical treatments to relieve symptoms.

38. Insemination: Insemination is a fertility treatment where sperm is introduced into the female reproductive tract to facilitate fertilization. It can be done through various methods, such as intrauterine insemination (IUI).

39. Insomnia: Insomnia is a sleep disorder characterized by difficulty falling asleep, staying asleep, or waking up too early. It can lead to daytime fatigue and affect overall well-being. Treatment options may include improving sleep hygiene and, in some cases, medications.

40. Insulin Pens: Insulin pens are devices used to administer insulin to individuals with diabetes. They provide an easy and convenient way to deliver insulin and can help manage blood sugar levels.

41. Insulin Resistance: Insulin resistance occurs when the body’s cells become less responsive to insulin, leading to high blood sugar levels. It is a key factor in the development of type 2 diabetes and metabolic syndrome.

42. Interstitial Cystitis: Interstitial cystitis is a chronic condition characterized by bladder inflammation and pelvic pain. The cause is not well understood, and treatment often involves a combination of medications and lifestyle changes.

43. Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS): IC/BPS is another term used to describe interstitial cystitis, emphasizing the presence of bladder pain as a significant symptom.

44. Interstitial Lung Disease (ILD): ILD is a group of lung disorders characterized by inflammation and scarring of the lung tissues. It can lead to breathing difficulties and reduced lung function.

45. Interstitial Nephritis: Interstitial nephritis is a kidney disorder characterized by inflammation of the spaces between kidney tubules. It can be caused by various factors, including infections and medications.

46. Intertrigo: Intertrigo is a skin condition that occurs in skin folds, such as the armpits, groin, or under the breasts. It is characterized by red, irritated, and sometimes moist skin due to friction and trapped moisture. Keeping the affected area clean and dry and using topical creams can help alleviate symptoms.

47. Intestinal Obstruction: Intestinal obstruction is a blockage in the intestine that prevents the normal passage of food and fluids. It can be caused by various factors, such as adhesions, hernias, or tumors. Treatment may involve bowel rest, medications, or surgical intervention.

48. Intestinal Perforation: Intestinal perforation refers to a hole or tear in the intestine, allowing the contents to leak into the abdominal cavity. It is a serious medical emergency that requires immediate surgery to repair the perforation and prevent infection.

49. Intestinal Polyps: Intestinal polyps are small growths that can develop on the inner lining of the colon or rectum. While most polyps are benign, some can become cancerous over time. Regular screenings and removal of polyps can help prevent colorectal cancer.

50. Intracerebral Hemorrhage: Intracerebral hemorrhage is a type of stroke that occurs when a blood vessel ruptures within the brain, causing bleeding and damage to brain tissues. It is a medical emergency that requires prompt intervention to reduce brain damage.

51. Intracranial Aneurysm: An intracranial aneurysm is a bulging and weakened area in the wall of a blood vessel in the brain. If it ruptures, it can lead to a potentially life-threatening condition called subarachnoid hemorrhage. Treatment may involve surgery or endovascular coiling to prevent rupture.

52. Intracranial Hypertension: Intracranial hypertension, also known as pseudotumor cerebri, is a condition where the pressure inside the skull increases without a clear cause. It can lead to headaches, vision problems, and other neurological symptoms.

53. Intraductal Carcinoma: Intraductal carcinoma refers to a type of breast cancer that originates in the milk ducts. It is an early-stage cancer, and treatment typically involves surgery, radiation, and hormone therapy.

54. Intraductal Papillary Mucinous Neoplasm (IPMN): IPMN is a type of pancreatic cyst that can potentially progress to pancreatic cancer. Regular monitoring and, in some cases, surgery are recommended to manage IPMN.

55. Intraductal Papilloma: Intraductal papilloma is a non-cancerous breast tumor that grows in the milk ducts. While usually benign, it can cause nipple discharge and may require surgical removal for diagnosis and symptom relief.

56. Intrahepatic Cholestasis of Pregnancy (ICP): ICP is a liver disorder that occurs during pregnancy, leading to reduced bile flow and elevated bile acids in the blood. It can cause itching and, in severe cases, increase the risk of preterm birth. Management may involve medications and early delivery.

57. Intrauterine Growth Restriction (IUGR): IUGR is a condition where a fetus fails to grow at the expected rate during pregnancy. It can be caused by various factors and may increase the risk of complications for the baby. Close monitoring and appropriate management are essential.

58. Intussusception: Intussusception is a condition where one part of the intestine slides into the adjacent section, causing a blockage. It primarily affects infants and young children and requires immediate medical attention to prevent complications.

59. Invasive Ductal Carcinoma (Breast Cancer): Invasive ductal carcinoma is the most common type of breast cancer, where cancer cells grow outside the milk ducts into the surrounding breast tissues. Treatment may involve surgery, chemotherapy, radiation, and targeted therapies.

60. Invasive Haemophilus Influenzae Disease: Invasive Haemophilus influenzae disease is caused by the bacterium Haemophilus influenzae and can lead to various infections, including meningitis, pneumonia, and septicemia. Vaccination can help prevent this disease.

61. Invasive Meningococcal Disease: Invasive meningococcal disease is caused by the bacteria Neisseria meningitidis and can lead to severe infections, including meningitis and septicemia. Vaccination is crucial to prevent this life-threatening disease.

62. Invasive Pneumococcal Disease: Invasive pneumococcal disease is caused by the bacterium Streptococcus pneumoniae and can lead to pneumonia, meningitis, and bloodstream infections. Vaccination is essential for preventing this disease.

63. Iritis: Iritis is inflammation of the iris, the colored part of the eye, which can cause eye pain, redness, and sensitivity to light. Prompt treatment with eye drops or medications is essential to prevent complications.

64. Iron Deficiency: Iron deficiency is a common nutritional deficiency, often caused by inadequate iron intake or absorption. It can lead to anemia and fatigue, and treatment typically involves iron supplements and dietary changes.

65. Iron Deficiency Anemia: Iron deficiency anemia is a type of anemia that occurs when the body lacks sufficient iron to produce hemoglobin. It can lead to symptoms such as weakness, pale skin, and shortness of breath.

66. Iron Overload Disorder: Iron overload disorder, also known as hemochromatosis, is a condition where the body absorbs and stores too much iron. This can lead to organ damage and may require regular blood removal (phlebotomy) to manage iron levels.

67. Irritable Bowel Syndrome (IBS): IBS is a common gastrointestinal disorder characterized by abdominal pain, bloating, and changes in bowel habits. While the exact cause is unknown, management often involves dietary changes and stress reduction.

68. Irritable Hip: Irritable hip, also known as transient synovitis, is a common cause of hip pain in children. It is usually self-limiting and resolves without specific treatment.

69. Ischemic Heart Disease: Ischemic heart disease, also known as coronary artery disease, occurs when there is reduced blood flow to the heart muscles due to narrowed or blocked coronary arteries. Lifestyle changes, medications, and interventions like angioplasty may be used to manage this condition.

70. Ischemic Stroke: Ischemic stroke occurs when a blood clot blocks a blood vessel in the brain, leading to reduced blood flow and brain damage. Prompt medical intervention, such as thrombolytic therapy, is crucial to restore blood flow and minimize brain injury.

71. Islet Cell Tumor: Islet cell tumors are rare tumors that develop in the pancreas and produce hormones, such as insulin and glucagon. Depending on the type of tumor, treatment may involve surgery, medications, or other interventions.

72. Itching: Itching, also known as pruritus, is a common symptom that can result from various skin conditions, allergies, or systemic diseases. Identifying and treating the underlying cause can help alleviate itching.

73. Itchy Bottom: An itchy bottom, also known as pruritus ani, is a common condition characterized by itching and discomfort around the anus. It can be caused by various factors, including poor hygiene, skin conditions, or certain infections. Proper anal hygiene, avoiding irritants, and using topical treatments can help relieve itching and discomfort.


I hope you found this article “Diseases That Start With I” helpful and got insights into some of the rare and lesser-known medical conditions.

Also, keep in mind that, this isn’t an exhaustive list, if there are any Diseases starting with the letter I.

Feel free to leave a comment below with the missing Disease and I’ll update the list as soon as possible.

And, if you’d like to explore more Diseases starting with different letters of the alphabet, click the link below:

  • Diseases That Start With J
  • Diseases That Start With K
  • Diseases That Start With L
  • Diseases That Start With M

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