60-year-old male patient who refers 10 days ago the appearance of blistering lesions on dorsum of hands after sun exposure. The picture is accompanied by skin fragility. Histopathologically there is a subepidermal blister with PAS+ deposits in and around the superficial dermal vessels. The most plausible diagnosis is:
Porphyria cutanea tarda (PCT) is the most common porphyria and can present with three major clinical forms: familial, sporadic and toxic. Clinically, it is characterized by marked skin fragility with the appearance of erosions, vesicles and blisters after minimal trauma. The most frequent sites are the back of the hands and the face, i.e. the areas of greatest photoexposure. Clinically, the most important differential diagnosis should be established with pseudoporphyria or phototoxic bullous dermatitis, in which the blisters and cutaneous erosions are produced by photosensitivity, induced by drugs such as tetracyclines, sulfonamides, etc. However, unlike porphyria, porphyrin levels in serum, feces and urine are normal. The histopathological differential diagnosis should be established with those diseases showing dermal hyaline deposits, such as: hyalinosis cutis, in which unlike porphyria, PAS-positive hyaline deposits are extensive and massively occupy the deep dermis and subcutaneous cellular tissue; Milium colloid in which hyaline material, usually PAS negative expands the papillary dermis, forming characteristic clefts and fissures; and lipoid proteinosis, in which the material is deposited throughout the dermis, has a distribution not only perivascular but more extensive than in porphyria, and usually affects sweat glands.
Familial benign pemphigus.
Pemphigoid.
Porphyria cutanea tarda.
Pemphigus vulgaris.
Scalded skin syndrome.
Porphyria cutanea tarda (PCT) is the most common porphyria and can present with three major clinical forms: familial, sporadic and toxic. Clinically, it is characterized by marked skin fragility with the appearance of erosions, vesicles and blisters after minimal trauma. The most frequent sites are the back of the hands and the face, i.e. the areas of greatest photoexposure.