What symptom is characteristic of porphyria cutanea tarda related to sunlight exposure?

The characteristic symptom of porphyria cutanea tarda related to sunlight exposure is the formation of vesicles and blisters on sun-exposed areas of the skin. This condition is a type of porphyria that results from a deficiency in the enzyme uroporphyrinogen decarboxylase, leading to an accumulation of porphyrins in the liver and skin.

When the skin is exposed to sunlight, particularly ultraviolet (UV) light, these accumulated porphyrins can react with the light and cause damage to the skin cells, resulting in blistering and the formation of vesicles. The damage is particularly pronounced in areas often exposed to the sun, such as the back of the hands and face.

In contrast, reduced skin pigmentation, increased hair growth, and development of skin tags are not commonly associated with porphyria cutanea tarda or its photosensitivity. These features do not arise as a reaction to sunlight exposure in the context of this specific type of porphyria. Thus, the formation of vesicles and blisters is the defining symptom that directly correlates with sunlight exposure in individuals with this condition.