## **Core Concept**
Lathyrism is a condition caused by consuming a specific type of legume that contains a toxin harmful to humans. The condition affects the nervous system and can lead to spastic paraparesis or quadriparesis. The toxin responsible is known as ODAP (oxalyldiaminopropionic acid) or BOAA (β-N-oxalyl-L-α,β-diaminopropionic acid).

## **Why the Correct Answer is Right**
The correct answer, **C. Lathyrus sativus**, also known as grass pea or chickling pea, is the legume associated with lathyrism. When consumed in large quantities over time, particularly during famine periods when other food sources are scarce, it can lead to neurolathyrism. The toxin in Lathyrus sativus, BOAA, acts by inhibiting the enzyme glutamate dehydrogenase and affecting the neurotransmitter glutamate, leading to neuronal damage.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While some species of *Lathyrus* can be toxic, **Lathyrus odoratus** (sweet pea) primarily causes osteolathyrism, a different condition characterized by skeletal abnormalities, not neurolathyrism.
- **Option B:** *Phaseolus* species, like the kidney bean, are not associated with lathyrism.
- **Option D:** *Vicia* species, including the common vetch, are not typically associated with neurolathyrism.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that neurolathyrism is preventable by avoiding the consumption of *Lathyrus sativus* as a staple food, especially during famine periods. Early symptoms include back pain, stiffness of the legs, and weakness, progressing to spastic paraparesis.

## **Correct Answer:** . Lathyrus sativus