Porphyria Cutanea Tarda is a Biochemical and Not Histological Diagnosis

Abstract

Porphyria cutanea tarda is the most common porphyria, due to acquired deficiency of hepatic uroporphyrinogen decarboxylase (UROD) enzyme, presenting with photosensitivity and blistering skin lesions. Factors making an individual susceptible to PCT include alcohol consumption, smoking, hepatitis C, HIV, estrogen use, and UROD mutation. Diagnosis of PCT is made with typical porphyrin profile of elevated plasma porphyrins (maximum fluorescence at 620 nm) and urine porphyrins (predominant hexa-, penta-, hepta- carboxyporphyrins). Skin biopsy may show features consistent with PCT, however by themselves may not be diagnostic. PCT is readily treatable with either phlebotomy schedule or low dose hydroxychloroquine regimen. We present two cases referred to our centre, all of them diagnosed with PCT based on a skin biopsy. An 81 year old man presented with blistering skin lesions and photosensitivity on dorsal hands and scalp. Skin biopsy from dorsal hand performed by his dermatologist showed dilated blood vessels in dermis with collagen deposition, consistent with PCT. He had no susceptibility factors for PCT. The porphyrin profile was normal with plasma porphyrins of 0.1 mcg/dl (normal <0.9) and urine porphyrins of 35 nmol/L (normal <300). A 28 year old female was diagnosed with PCT based on skin biopsy. She had 4 year history of photosensitivity and plaque like lesions on dorsal hands, which were progressive in spite of being treated with hydroxychloroquine. Except history of smoking, she had no other susceptibility factors of PCT. Biochemical porphyrin profile was normal. She is being treated for pseudoporphyria secondary to doxycycline and is doing well. Conclusions: Biochemical porphyrin profile and not skin histology is the confirmatory test for the diagnosis of PCT