Asymptomatic Hyperpigmentation without Preceding Inflammation as a Clinical Feature of Citrus Fruits-Induced Phytophotodermatitis

Abstract

Phytophotodermatitis is a condition that occurs by contact with plants containing phototoxic agents such as furocoumarins and psoralens with subsequent ultraviolet exposure. Phytophotodermatitis typically presents as sharply defined erythematous patches with occasional blistering, sometimes accompanied with pain or itching sensation. In some cases, however, sudden appearance of asymptomatic hyperpigmentation can be the only clinical finding of phytophotodermatitis. Here, we present two patients with sudden development of asymptomatic pigmentation on their hand without preceding inflammation by the contact with citrus fruits containing photosensitizers and subsequent exposure to strong sunlight. As like these patients, phytophotodermatitis can present with only pigmentation without noticeable inflammation especially in dark skinned people. In such cases, physician can sometimes have difficulty in diagnosis of phytophotodermatitis. Therefore, it is important to consider the possibility of phytophotodermatitis through careful history taking, especially in patients who have abruptly developed well-defined hyperpigmentation on sun-exposed areas, to avoid unnecessary test and treatment.

Keywords: Citrus fruits; Lime; Phytophotodermatitis; Pigmentation.

Fig. 1. (A) Multiple brown pigmented patches on the left hand. (B) On the lateral sides of fingers, pigmentations showed irregular shape with rather sharp borders. (C) Some pigmentation showed reticulated pattern.

Fig. 2. (A) Multiple brown pigmented patches on the left hand. (B) Homogeneous brown colored pigmentations with rather straight borders were observed on the lateral sides and the dorsum of fingers. (C) Some pigmentations showed overlying scales.

Fig. 3. (A) Skin biopsy specimen from case 1. (B) Skin biopsy specimen from case 2. Both skin tissues showed slightly increased number of melanocytes and basal hyperpigmentation (H&E; A, B: ×200).

Fig. 4. (A) Schematic design of photoprovocation test and back skin of a healthy adult male. Skin was split into untreated (negative) and lime extract applied area. The 5, 10, 20, and 30 J/cm² of ultraviolet A (UVA) were irradiated on the back. (B) Three days and six days after UVA irradiation. Brown colored, homogeneous pigmented macules are observed.