PD11 Simultaneous development of photosensitivity in a father and daughter: de novo or exposure induced?

• Published in: British journal of dermatology (1951) Vol. 191; no. Supplement_1; p. i86
• Main Authors: Ross, Hannah, Parkin, Donna, Ayer, Jean
• Format: Journal Article
• Language: English
• Published: 28-06-2024
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1093/bjd/ljae090.175

Chronic actinic dermatitis and photoaggravated eczema are rare photosensitivity disorders that, while considered to be immunologically mediated, usually develop de novo. A 4-year-old White British girl and her 33-year-old White British father presented to a tertiary photobiology clinic with similar photodistributed eruptions that occurred acutely following exposure to an airborne glyphosate organophosphate-containing weedkiller. The eruptions persisted thereafter on exposure to sunlight. Approximately 15 min of sun exposure is sufficient to provoke a red, scaly and blistering eruption around 6–12 h later. The eruption affects only photoexposed sites, including the posterior neck, elbows, dorsal hands and cheeks, and episodes persist for several days. The father underwent monochromated light testing to narrowband widths of ultraviolet (UV)B, UVA and visible radiation and demonstrated exquisite photosensitivity. Provocation testing to broadband UVA and a solar simulator were abandoned after the first exposure due to a significant erythemal and oedematous response. The daughter underwent modified monochromator testing due to her age, but similarly demonstrated significant photosensitivity with reduced thresholds from 300 to 370 nm. Reduced-dose provocation with broadband UVA and a solar simulator resulted in a mild, blotchy, papular erythema. Several months later, both father and daughter reported worsening of their photosensitivity. Repeat photoinvestigation carried out 15 months following the initial exposure to the glyphosate, suspected to be the precipitant, showed an objective deterioration in photosensitivity in both patients, resulting in formal diagnoses of chronic actinic dermatitis. Reports of phototoxicity after contact with glyphosate formulations are exceedingly rare. However, there is a report of the preservative coformulant benzothiazolinone (BIT), found in glyphosate formulations, that was confirmed to be phototoxic through exposure of the skin for 24 h followed by UVA exposure (Hindson C, Diffey B. Phototoxicity of glyphosate in a weedkiller. Contact Dermatitis 1984; 10: 51–2.) The reported papulovesicular eruption that followed BIT and UVA exposure is in keeping with the eruption seen in our patients. However, photopatch testing to BIT was negative in both patients. There are no other reports in the literature of photosensitization following organophosphate exposure with prolonged and worsening effects 15 months after exposure. Therefore could it be possible that two de novo cases have occurred in one family at exactly the same time, or could the initial phototoxic reaction have triggered an immune response that has subsequently caused the development of chronic actinic dermatitis?