Medical conditions that can lead to dark knuckles include:
1. Acanthosis Nigricans: Acanthosis nigricans (AN) is a skin condition that causes small patches of skin, often near the knuckles, to darken, thicken, and become velvety to the touch. AN often takes months or years to appear, and it can cause the skin to have a bad odor or itch.
Other areas where AN develops include: armpits, neck, groin area, elbows, knees, bellybutton, beneath the breasts, face, female genitalia.
AN is not contagious or harmful on its own, but it can be a precursor to other medical issues, such as: - Prediabetes or diabetes: Prediabetes means that a person’s blood sugar levels are higher than normal. If a doctor is able to identify prediabetes early, a person may be able to prevent full diabetes from developing by making lifestyle changes. - Hormonal conditions: AN can also signal a thyroid or adrenal condition or a hormonal imbalance, such as polycystic ovary syndrome (PCOS). PCOS causes females to produce too much testosterone, leading to fertility issues, pelvic pain, acne, weight gain, and menstrual irregularities.
Cancer: If AN develops suddenly, it may be a sign of cancer, particularly cancer of the stomach, liver, or colon.
2. Dermatomyositis: Dermatomyositis is a rare disease that causes muscle weakness through chronic muscle inflammation. One of the first and most recognizable symptoms is a patchy bluish-purple or red rash in areas of skin covering the muscles near the joints. These include the muscles near the knuckles, elbows, heels, and toes.
3. Addison’s disease: Addison’s disease is an autoimmune condition in which the body mistakenly attacks the adrenal glands, resulting in low levels of cortisol and aldosterone.
An initial symptom of Addison’s disease is areas of darker skin near scars and skin creases, such as the knuckles. This discoloration provides an early clue, as it can develop months or years before any other symptoms. (Cont'd in the comment section)