Case Study - A blistered hand

Diagnosing an interesting skin presentation. By Dr Sidhu Gada

Phytophotodermatitis can be managed with oral antihistamines (Author image)
Phytophotodermatitis can be managed with oral antihistamines (Author image)

A man presented to the surgery with blisters on his hand. A history of the past few days was taken, including asking about bites, new medicines, topical lotions used and any activities.

The patient explained he had been gardening a couple of days before and handled fig leaves. After ruling out other possibilities we reached the diagnosis of phytophotodermatitis.

It was managed with oral steroids and antihistamines, which helped to clear the skin presentation. At follow-up, he still had pigmentation in the affected region, which we hoped would fade over the next few weeks.

In my practice in the past few years, I have seen a couple of cases of phytophotodermatitis, so I don't think it is a rare condition, but a high degree of suspicion and a detailed history are required to pick up uncommon conditions like these.

Phytophotodermatitis

Phytophotodermatitis is a cutaneous, phototoxic, inflammatory, non-immunological response resulting from contact with light-sensitising botanical substances. The term phytophotodermatitis was first used in 1942 by Klaber.1

Several plant families, including the Rutacea, Moraceae, Leguminosae and Rosaceae families, contain species that may cause phytophotodermatitis. The fig tree belongs to the Moraceae family. The photosensitising element of the plant is furocoumarin (psoralen).

In the skin, the psoralen causes cellular damage upon excitation by UVA radiation.

The damage is caused either by direct reaction of sensitised psoralen with cell DNA or by indirect damage through creation of reactive oxygen species.

The geographical location, seasonal variations, humidity and plant fungal infections can all alter the level of furocoumarin in a given plant.2

The primary skin lesions may become erythematous or form vesicles or bullae. Hyperpigmented patches without a preceding erythematous phase have also been reported and the hyperpigmentation may persist up to six months after exposure.3 The site of the lesion is restricted to the site of contact with fluorochromes and exposure to sunlight.

Phytophotodermatitis is a clinical diagnosis. Photo-patch testing in such patients is contraindicated, because a positive response might be severe. Rarely, in cases where diagnosis is difficult, a skin biopsy can be performed.

Differential diagnosis

The differential diagnosis includes irritant or allergic contact dermatitis. History is vital for making the correct diagnosis. Physicians need to be aware of the condition especially in cases with exposure to botanical stimuli and in summer months, when UVA intensity is high.

There are case reports where phytophotodermatitis was confused with child abuse.3

Phytophotodermatitis is a self-limiting problem. Oral or topical steroids along with antihistamines can be used during acute eruptions. Patients can be advised to avoid contact with the agent by using gloves and protective clothing in future.

  • Dr Gada is a GP principal in Ipswich, Suffolk

References
1. Klaber R. Phytophotodermatitis. BrJ Dermatol 1942; 54: 193-211.

2. Deleo VA. Photocontact dermatitis. Dermatol Ther 2004; 17: 279-88.

3. Hill PF, Pickford M, Parkhouse N. Phytophotodermatitis mimicking child abuse. J R Soc Med 1997; 90: 560-1.

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