Experimental phytophotodermatitis was produced using homogenates from different parts of Heracleum laciniatum and long-wave ultraviolet light. The homogenates of leaves and flowers produced strong phototoxic reactions, fruit slightly less. Stems were either non-phototoxic or only slightly phototoxic. The roots of young plants did not evoke photosensitivity reactions, whereas the roots of older plants were strongly phototoxic; even roots collected from the frozen ground in December elicited strong reactions. Abdominal and midback skin were more photosensitive than skin of the lateral aspects of the underarms and legs.

Background: Case reports display similaritiesbetween multiple sclerosis and acute intermittent porphyria (AIP). This study examines whether patients with AIP in general demonstrate white-matter lesions on brain magnetic resonance imaging (MRI) and/or abnormalities in plasma and/or cerebrospinal fluid (CSF) when examined outside attacks. We looked particularly for the presence of oligoclonal bands (OB) of immunoglobulin (Ig) in liquor. Methods:Eight AIP gene carriers without previous episodes of porphyria, mean age 42.8 years (range 30–60), and 8 AIP gene carriers with previous episodes of porphyria, mean age 42.8 years (range 33–62), were examined with brain MRI, venous blood samples and lumbar punctures. Results: Two male AIP gene carriers with previous episodes of porphyria, 58 and 35 years of age, had multiple white-matter, high-signal lesions on T₂- weighted MRI sequences. Two AIP gene carriers without previous episodes of porphyria, 1 male and 1 female, had less than 5 such lesions. No OB were seen in the CSF in any patient, but 1 carrier had an increased level of protein in the CSF. Seven of 16 subjects (44%) had increased levels of HbA1c (>6.0), suggesting protracted hyperglycemia, and 3 further subjects had borderline levels (5.9). Conclusion: T₂-weighted MRI sequences demonstrated multiple white-matter, high-signal lesions in 4 out of 16 AIP gene carriers (25%). No carrier demonstrated OB of Ig in CSF, making it unlikely that demyelinating lesions play a pivotal role in the pathogenesis of CNS symptoms in AIP. Only 1 AIP gene carrier had an increased level of protein in CSF; this contrasts with studies during acute attacks of porphyria. Seven subjects (44%) had abnormally high levels of HbA1c, in spite of the fact that no patient had a previous diagnosis of diabetes mellitus.

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Phytophotodermatitis from Heracleum laciniatum is described in 2 typical cases. Experimental phytophotodermatitis was produced using homogenates from leaves of the plant and long-wave ultraviolet light. The homogenates of leaves produced strong phototoxic reactions. The minimal phototoxic erythema dose was determined to be lowest for abdominal and midback skin. The action spectrum for Heracleum laciniatum homogenates applied topically was found to be in the range 315-375 nm with peak sensitivity at 330-335 nm.