Porphyria Cutanea Tarda: Location of Skin Lesions
Porphyria cutanea tarda (PCT) skin lesions characteristically present on sun-exposed areas, particularly the dorsal hands and face. 1, 2
Primary Sites of Involvement
The hands are the most commonly affected site, with typical cutaneous lesions including bullae, erosions, and skin fragility developing on the dorsal surfaces of the hands and fingers. 1, 2 The face is the second most frequent location for PCT manifestations. 1, 2
Additional Sun-Exposed Areas
Beyond the hands and face, PCT lesions can develop on other sun-exposed regions including:
- Forearms - particularly the extensor surfaces 3, 4
- Neck and neckline - where sclerodermatous changes may occur in some patients 5
- Upper back and shoulders - especially in patients with significant sun exposure 5
Clinical Presentation Pattern
The distribution follows a strict pattern of photoexposure, as PCT results from accumulation of phototoxic porphyrins in the skin that cause damage following exposure to light between 400 and 410 nm wavelengths. 1 This explains why lesions are consistently found on areas that receive the most direct sunlight during daily activities. 6, 7
Blisters and erosions develop acutely on these sun-exposed areas, often accompanied by skin fragility, hypertrichosis (particularly facial/malar), abnormal pigmentation, and milia formation. 4, 6 Some patients describe the severity as having "huge blisters" with "skin falling off" in affected areas. 6
Important Clinical Caveat
Not all PCT patients present with blisters - some may develop sclerodermatous changes on the neck, face, and neckline as the initial or only cutaneous manifestation, which can delay diagnosis if clinicians are not aware of this variant presentation. 5 In these cases, the diagnosis must still be suspected based on the sun-exposed distribution pattern combined with abnormal liver tests and elevated porphyrin levels. 5