Pellagra is a skin disease caused by a deficiency of niacin (vitamin B3) in the diet. It is characterized by various symptoms, including dermatitis, diarrhea, dementia, and death if left untreated. The correct answer is option 'D' - Pellagra.

Below is a detailed explanation of why Pellagra is a skin disease:

Heading: Pellagra - A Skin Disease

Pellagra is a skin disease caused by a deficiency of niacin (vitamin B3) in the diet. It primarily affects areas of the skin exposed to sunlight, such as the face, neck, hands, and feet. The term "pellagra" comes from the Italian words "pelle" (skin) and "agra" (rough), referring to the rough and scaly skin lesions that are characteristic of the condition.

Heading: Symptoms of Pellagra

Pellagra presents with a variety of symptoms, including:

1. Dermatitis: Pellagra causes a characteristic dermatitis, which is a skin inflammation. The affected areas may be red, scaly, and itchy. The skin may become rough and thickened over time.

2. Diarrhea: Pellagra can also lead to gastrointestinal symptoms, including chronic diarrhea. The diarrhea may be severe and persistent, leading to dehydration and electrolyte imbalances if left untreated.

3. Dementia: In advanced cases, pellagra can affect the nervous system and lead to cognitive impairment. Symptoms may include confusion, memory loss, irritability, and even psychosis.

4. Other symptoms: Pellagra can also cause fatigue, loss of appetite, weight loss, and sensitivity to sunlight.

Heading: Causes and Risk Factors

Pellagra is caused by a deficiency of niacin in the diet. Niacin is an essential nutrient that plays a crucial role in the metabolism of carbohydrates, fats, and proteins. It is found in various foods, including meat, fish, poultry, legumes, and grains.

Certain factors can increase the risk of developing pellagra, including:

1. Poor diet: Individuals who have a diet that is low in niacin-rich foods are at a higher risk.

2. Alcoholism: Alcohol can interfere with niacin absorption and increase the risk of pellagra in heavy drinkers.

3. Malabsorption disorders: Certain medical conditions, such as Crohn's disease, celiac disease, and gastrointestinal surgeries, can impair the absorption of niacin and increase the risk of deficiency.

Heading: Treatment and Prevention

The treatment for pellagra involves addressing the underlying niacin deficiency. This can be achieved through dietary changes and niacin supplementation. Increasing the intake of niacin-rich foods or taking niacin supplements can help alleviate the symptoms and prevent further complications.

Prevention of pellagra involves maintaining a well-balanced diet that includes adequate amounts of niacin. It is important to consume a variety of foods from different food groups to ensure sufficient intake of all essential nutrients, including niacin.

In conclusion, pellagra is a skin disease caused by a deficiency of niacin in the diet. It is characterized by dermatitis, diarrhea, and dementia if left untreated. Prompt diagnosis and appropriate treatment can help alleviate the symptoms and prevent complications.