Addison's disease, also known as primary adrenal insufficiency, is a rare but serious endocrine disorder where the adrenal glands do not produce sufficient steroid hormones, particularly cortisol and aldosterone. It can occur at any age and affects both sexes equally. The condition is usually caused by an autoimmune response where the body's immune system mistakenly attacks and damages the adrenal glands, leading to their inability to produce hormones efficiently. Symptoms of Addison's disease develop gradually and can include chronic fatigue, muscle weakness, weight loss, low blood pressure, and hyperpigmentation of the skin. One of the hallmark features of Addison's disease is an increased pigmentation of the skin, particularly in areas exposed to friction or pressure, and in the creases of the palms. Patients may also experience salt cravings due to the lack of aldosterone, which helps regulate sodium and potassium in the body. Because cortisol plays a vital role in various bodily functions, including metabolism, immune response, and stress response, its deficiency can lead to a range of symptoms and increase susceptibility to infections. Addison's disease can lead to an Addisonian crisis, a life-threatening medical emergency characterized by severe pain, vomiting, diarrhea, low blood pressure, and loss of consciousness. This crisis can be triggered by stress, illness, or injury and requires immediate medical attention. Diagnosis of Addison's disease is typically based on clinical symptoms, blood tests showing low cortisol levels, and ACTH stimulation tests. Treatment involves lifelong hormone replacement therapy to substitute the deficient hormones, primarily with corticosteroids like hydrocortisone, and, in some cases, fludrocortisones for aldosterone replacement. Patients with Addison's disease must be vigilant about managing their condition, particularly during periods of stress or illness, and they often carry emergency medication or wear a medical alert bracelet for rapid treatment in case of an Addisonian crisis.