The thiamin deficiency disease is characterized by weakness, poor muscular coordination, and decreased functioning of the cardiovascular and nervous systems.

The disease caused by thiamin deficiency is known as Beriberi. Here are the steps that characterize this disease:

1. Weakness: The first symptom of Beriberi is usually weakness, especially in the lower limbs. This is due to the lack of thiamin, which is essential for energy production in the body.

2. Poor muscular coordination: As the disease progresses, the patient may experience poor muscular coordination. This is because thiamin is necessary for the proper functioning of the nervous system, which controls muscle movement.

3. Decreased functioning of the cardiovascular and nervous systems: If left untreated, Beriberi can lead to serious complications such as heart failure and neurological disorders. This is due to the decreased functioning of the cardiovascular and nervous systems, which are both affected by thiamin deficiency.

In conclusion, Beriberi is a serious disease that can lead to life-threatening complications if not treated promptly. It is therefore important to ensure adequate intake of thiamin through a balanced diet or supplementation.