Clinical Experience
IgE-mediated reactions
Blue vetch may uncommonly induce symptoms of food allergy and occupational allergy in sensitised individuals.
Sera from 38 Spanish legume-sensitised patients were used to assess the allergenic composition of Blue vetch. Seventy-seven percent of patients showed a positive skin test to Blue vetch flour; 4 of these patients had developed clinical symptoms in relation to Blue vetch, and 2 of them, in addition, to other legumes (3).
A study reports on a 10-year-old child with asthmatic attacks related to Lathyrus sativus flour inhalation. This child had a history of perennial rhinitis, and bronchial asthma was reported. In the previous year, shortly after exposure to Blue vetch flour in the family store, he had experienced sneezing, rhinorrhoea, wheezing and dyspnoea attacks. Avoiding exposure resulted in a marked reduction of symptoms, and he became asymptomatic. He tolerated the ingestion of foodstuffs prepared from this legume, as well as exposure to other types of flours. Skin test with the raw extract was positive, and negative for the heated extract. Specific bronchial provocation challenge was markedly and immediately positive. IgE antibodies to Lathyrus sativus flour were demonstrated by indirect enzyme immunoassay. The authors suggest that the loss of allergenic sensitivity observed in the cutaneous test with heated Blue vetch may indicate the reason this patient was able to ingest cooked foodstuffs prepared with this flour without reacting (13).
Two young women experienced symptoms after eating Blue vetch. They reported previous hypersensitivity to other legumes (14).
Generalised urticaria and facial oedema in a 5-year-old, occurring a few minutes after ingestion, have been reported (15).
Occupational asthma has been reported following exposure to flour made from Blue vetch. This flour is used in the industrial processing of parquet (wood flooring). A 55 years old man is described, who reported a one year long history of rhinorrhoea, paroxysmal sneezing, eyes and nasal pruritus, and wheezing dyspnea with coughing and chest tightness, symptoms which were related to his working with Blue vetch flour. Symptoms abated during holidays and weekends. He had worked in direct contact with Blue vetch flour for 15 years, which involved the production of a sealant for wooden floor panels. He had never eaten Blue vetch and did not experience adverse effects ingesting other legumes. Skin prick test with the extract showed a positive immediate response. IgE antibody level to grass pea was 9.57 kUA/l. Specific bronchial challenge test elicited an immediate response, both clinically (rhinitis, cough, dyspnoea, chest tightness) and with a 20% decrease in FEV1 at 5 minutes (2).
A 42-year-old man was described who had worked as a carpenter for 6 years and who reported a history of rhinorrhoea, paroxysmal sneezing, nasocular pruritus, lacrimation, wheezing and dyspnoea attacks while preparing a mixture to seal the junctures between wooden panels. Skin prick tests with Blue vetch and Lentil extracts were positive. IgE antibody level to Blue vetch was 0.62 kUA/l. Histamine release tests were positive. Bronchial challenge with Blue vetch was positive within 5 minutes, with a decrease in FEV1 of 20%. He also developed rhinoconjunctivis. The authors point out that in cases of occupational asthma to Blue vetch flour, patients tolerate the cooked food (16). As suggest by other authors as well, some or all allergens in Blue vetch are heat-labile, resulting in Blue vetch-allergic individuals being able to ingest cooked Blue vetch products (13).
Occupational asthma to a close relative, Sweet pea (Lathyrus odoratus), has also been described (17).
Other reactions
Neurolathyrism is a neurological condition seen among people who eat the seeds of Lathyrus sativus as a principal source of food energy for 2 months or more. It is characterised by severe muscular rigidity and irreversible spastic paralysis of the lower limbs, spinal hyperreflexia, and structural changes of the skeleton and connective tissue (18-19). Once prevalent throughout Europe, N. Africa, the Middle East and parts of the Far East, the disease is presently restricted to India, Bangladesh and Ethiopia (20). The biochemical mechanism involves beta-N-Oxalyl amino-L-alanine (L-BOAA); a synonym is beta-N-oxalyl-alpha,beta-diaminopropionic acid (beta-ODAP). This is a naturally occurring non-protein amino acid present in Blue vetch. Ingestion of L-BOAA in a staple diet results in a progressive neurodegenerative condition, a form of motor neuron disease that affects the upper motor neurons and anterior horn cells of the lumbar spinal cord. L-BOAA is an excitatory acid and acts as an agonist at the AMPA receptor (21-22).
The oil from the seeds is a powerful and dangerous cathartic that contains a poisonous principle, probably an acid salt of phytic acid.
