Description, Causes and Risk Factors:
A condition clinically identical to porphyria but with no abnormality in porphyrin excretion, consequent to drug ingestion or hemodialysis.
Pseudoporphyria (PP) is a bullous dermatoses caused by phototoxicity that affects chronic renal failure patients on peritoneal dialysis or hemodialysis. Its clinical and histopathological changes are similar to chronic hepatic porphyria cutanea tarda. Other factors such as drugs, tanning beds, PUVA, were also connected with the etiology of Pseudoporphyria. Except for the suspension of the causative agents and photo-protection, up to now, there is no treatment based on available evidence. There are reports of clinical control after the use of oral N-acetylcysteine.
The precise pathophysiologic mechanism of Pseudoporphyria is not fully understood. Some drugs, especially non steroidal anti-inflammatory drugs, can trigger pseudoporphyria in the presence of ultraviolet light. The Pathophysiology of pseudoporphyria associated with hemodialysis has not been fully explained. Aluminum hydroxide has been implicated in hemodialysis-associated pseudoporphyria. Aluminum hydroxide is found in dialysis solution and has been shown to produce a porphyria-like disorder after long-term administration in rats.
The prognosis is good for pseudoporphyria once the offending agent has been discontinued. However, it may take several months for all the skin lesions to resolve, and some patients are left with permanent scarring.
Skin signs include skin fragility and photosensitivity. Tense blisters form at the sites of minor trauma on sun-exposed skin, bursting early to leave scabs and erosions. The blisters are most often seen on the hands and feet. They sometimes heal with some scar formation and tiny white cysts under the skin (milia).
Of critical importance in the diagnosis of pseudoporphyria is the exclusion of true porphyria.The most important test is a serum/plasma porphyrin assay. If this result is negative, the patient does not have a true porphyria.If the serum/plasma porphyrin assay is unavailable, erythrocytes, urine, and stool may be evaluated for abnormal porphyrin levels.Other causes of photosensitivity, such as connective tissue disease, must be excluded by obtaining a serum antinuclear antibody titer and more specific studies.
Biopsies for histologic evaluation with hematoxylin and eosin stain and direct immunofluorescence should be performed. Serum samples may also be obtained for indirect immunofluorescence evaluation to aid in the exclusion of bullous pemphigoid.
It is important to withdraw the suspected agent where possible and avoid unnecessary exposure to strong light. Sun avoidance, avoidance of tanning booths, and usage of broad-spectrum sunscreen that blocks both UVA and UVB. Identification and avoidance of the offending drug.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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