A Histochemical Test for Citrulline: Adaptation of the Carbamido Diacetyl Reaction to Histologic Sections with Positive Results in Pilomatrixomas (Calcifying Epitheliomas)

The study investigated a histochemical test for detecting citrulline in hair follicle components, specifically the inner root sheath, which contained 6.1% citrulline by dry weight. Traditional methods using Ehrlich's reagent were less specific due to interference from tryptophan. The researchers adapted Fearon's diacetyl monoxime reagent for a more specific test, which involved a reaction in hot acid solution and used a silicone rubber adhesive to withstand boiling hydrochloric acid. This method successfully colored the inner root sheath bright orange and showed positive results in some keratinous areas of pilomatrixomas.