Lathyrism is a term describing a disease that develops after prolonged consumption of grass pea, known as Lathyrus sativus. The pathogenesis involves axonal degeneration of motor neurons and subsequent spastic paraparesis due to the introduction of neurotoxins from this food. The condition was rather common in Ethiopia, as well as India and surrounding countries, but is now rarely documented. The diagnosis rests on clinical criteria and findings obtained during history taking.
Lathyrism, considered to be a rare occurrence in clinical practice today, is a disease arising due to prolonged and excessive consumption of Lathyrus sativus legume, more commonly known as grass pea or chickling pea   . In limited concentrations, L. sativus is a part of the normal diet in many countries and lathyrism usually appears in times of profound famine from severe droughts or floods, as the legume can survive extremely dry conditions and tolerates floods as well   . Although previously documented throughout the world, three countries have reported the vast majority of cases in the previous decades - Ethiopia, Bangladesh, and India     . Lathyrism stems from ingestion of a neurotoxic excitatory beta-N-oxalylamino-L-alanine amino acid (BOAA) during droughts in very high amounts for at least a few months, and the term "staple diet" is often used to describe the excessive dietary intake of a certain food  . BOAA seems to directly promote symmetric degeneration of anterior horn cells and upper motor neurons in the spinal cord, as well as pyramidal cells responsible for leg movement located in the primary motor cortex   , with inhibition of mitochondrial activity being the presumable mechanism of disease . Consequently, the principal clinical manifestation of lathyrism is non-progressive spastic paraparesis of the lower limbs   . In addition to neurotoxic effects, some studies have identified bone pain as a symptom of lathyrism and marked skeletal changes on radiographic studies .
The diagnosis of lathyrism might be difficult to make without a properly obtained patient history and a complete neurological examination. A thorough nutritional assessment, during which ingestion of grass pea or chickling pea should be investigated, might be of critical importance, and some studies have confirmed that consumption of boiled or raw unripe grass pea significantly increases the risk of neurological symptoms . Because famine and droughts are regarded as necessary events for lathyrism to appear  , epidemiological data are equally useful in order to make a provisional diagnosis. For the still unknown reason, males more commonly suffer from lathyrism compared to females . The neurological assessment must include reflex testing and evaluation of movement, particularly of the lower extremities, and in the case of spastic paraparesis or even paralysis, clinical suspicion can be raised toward lathyrism. When bone pain is reported, plain radiography might be suggested, as skeletal deformities have been documented . As no specific tests exist, the diagnosis of lathyrism depends on the ability of the physician to recognize main signs of the disease and support those findings with information from the patient interview.