Calcium oxalate raphides

Abstract

DISTRIBUTION: Mostly exotic plants cultivated as garden- or pot plants. Zanthedeschia spp. occurs naturally in the wild in wet or moist places.BOTANICAL DESCRIPTION: These plants all belong to the family Araceae which are popular ornamental plants and include many beautiful house plants which are particularly grown for their decorative leaves, flowers and/or fruit.TOXIC PRINCIPLE: • Oxalic acid and in particular its insoluble calcium salt, occur in these plants. • Under influence of a high oxalic acid environment Ca-oxalate crystallises as the monohydrate salt in 250µ long, thin crystalline needles (raphides) with extremely sharp tips at both ends.MECHANISM OF ACTION: These needle-like crystals are loaded parallel in specialised, explosive, ampoule-shaped ejector cells (idioblasts) each with an operculum. These cells are situated on the edge of the surface stems and leaves. On pressure, such as crushing of the plant when chewed, the needle-like crystals are ejected and penetrate surrounding tissue resulting in intense irritation, discomfort and histamine release. This could probably be a defense mechanism of the plant to protect it from herbivores.SYNDROMES: Mechanical irritation.SYSTEMS AFFECTED: Gastro-intestinal system.CLINICAL SIGNS: A very unpleasant, transient stomatitis occurs when certain plants of the family Araceae are chewed by man, pets or livestock. It is especially a problem with puppies and children. • Discomfort to severe pain• Salivation • Paralysis of tongue • Dumb, numb feeling of mouth and throat • DysphagiaTREATMENT: Symptomatic treatment – this is a transient phenomenon. Corticosteroids. Antihistamines.