The porphyrias are a group of disorders of haem metabolism with deficiency in the enzymes of the haem biosynthetic pathway resulting in excess porphyrin production.1 Porphyria cutanea tarda (PCT) is the most common of eight subtypes with a predilection among black Southern Africans.1 Clinical manifestations are predominantly dermatological with photoactive porphyrins depositing in the skin causing bullae, hyper- and hypo-pigmentation, pseudoscleroderma, and hypertrichosis in sun-exposed areas.2 Sight-threatening ocular manifestations are rare and we describe a case of PCT presenting with corneal perforation and scleromalacia perforans.
A 54-year-old black female presented with a 6-week history of pain and loss of vision in the right eye, and progressive darkening and coarseness of her skin.
Examination revealed dark skin and sclerodermatous-like facial features (Figure 1). Visual acuity was hand movements right and 6/5 left. There were bilateral, symmetrical areas of punched out scleral thinning with choroidal show temporally in the interpalpebral fissures. The sclera was moderately inflamed in the right with a thin cornea, central perforation, and flat anterior chamber (Figure 2).
She had a tender hepatomegally and no systemic features suggestive of collagen-vascular disease.
Urine porphyrins were 14 035 nmol/l, serum iron 58.3 μmol and ferritin 1790 ng/l confirming a diagnosis of PCT and iron overload.
Treatment included oral prednisolone 60 mg daily and cyclosporine 2% drops QDS, avoiding topical steroids because of the risk of scleral perforation. Oral steroids were tapered and topical cyclosporine and lubricants continued. There has been steady improvement in scleral thickness and no sign of disease progression. The right eye is comfortable with a sclerosed cornea. She has undergone serial phlebotomy and is avoiding alcohol and sun exposure.
PCT is a hepatic porphyria characterised by deficient uroporphyrinogen decarboxylase activity and may be autosomal dominantly inherited or may occur sporadically.1 The predilection in black Southern Africans may be due to the increased incidence of haemochromatosis caused by ingestion of traditional tribal beer brewed in iron pots.1 Hereditary PCT is characterised by enzyme deficiency in all tissues while in acquired PCT, the deficiency is isolated to the liver and may be precipitated by external factors like iron overload, alcohol, and oestrogens.
Treatment involves avoidance of precipitating factors and UV exposure, while success has been achieved with phlebotomy and iron chelating agents.
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Zaborowski, A., Paulson, G. & Peters, A. Sight threatening complications in porphyria cutanea tarda. Eye 18, 949–950 (2004). https://doi.org/10.1038/sj.eye.6701362
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