Acute porphyrias: diagnosis and management

Porphyria syndrome associated with diabetic nephrosclerosis and erythropoietin

The porphyrias are inherited or acquired metabolic disorders caused by a partial deficiency in one of the enzymes of the heme biosynthetic pathway. Eight enzymes are utilized in the synthesis of heme. An enzyme defect in one of the last seven enzymes will result in one of the seven different forms of porphyria, some of which have similar signs and symptoms. This article describes six diabetic, azotemic patients with no prior history of porphyria, who developed a syndrome similar to acute intermittent porphyria after initiation of treatment with erythropoietin. One of the patients developed the syndrome predialysis, whereas the remaining patients were on maintenance hemodialysis. The symptoms varied but all resolved when erythropoietin was discontinued and reappeared in four cases when erythropoietin was restarted. In all of the patients, the enzyme aminolevulinic acid-dehydratase (ALA-D) was low and the uroporphyrinogen synthase was normal. This enzyme abnormality suggests an acquired form of delta-aminolevulinic acid dehydratase porphyria (ADP). Lead toxicity, succinylacetone, and zinc deficiency are known to depress ALA-D, but these conditions were not present. The development of the acute porphyria syndrome while the patients were receiving pharmacological doses of erythropoietin, which resolved when the drug was stopped, suggests that by stimulating heme synthesis, erythropoietin may unmask an enzyme deficiency resulting in the clinical expression of ADP. The patients responded favorably to a regimen that included discontinuation of erythropoietin, tight blood sugar control, maintaining the hematocrit above 30%, and a KT/V, a measure of dialysis adequacy, of 1.5 in the hemodialysis group. Plasmapheresis accelerated the recovery when used in two patients.

Pseudoporphyria as a result of voriconazole use: a case report

Voriconazole, a second-generation triazole, has recently been approved by the Food and Drug Administration (FDA) to treat invasive aspergillosis and refractory infections with Scedosporium apiospermum or Fusarium spp. The reported side-effects of voriconazole include visual changes, headaches, elevated hepatic enzymes, Steven-Johnson syndrome, toxic epidermal necrolysis, chelitis, photosensitivity, discoid lupus erythematosus and anaphylactoid infusion reactions. Pseudoporphyria was first described in association with nalidixic acid. It has the same clinical and histologic features as porphyria cutanea tarda (PCT) but is distinguished by normal porphyrin levels in the serum, urine and stool. We present the case of a patient who developed pseudoporphyria after receiving treatment with voriconazole.

Quantitative Measurement of Porphobilinogen in Urine by Stable-Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry

Background: Measurement of porphobilinogen (PBG) is useful in the diagnosis of the acute neurologic porphyrias. Currently used colorimetric assays lack analytical and clinical sensitivity and specificity.

Methods: We developed a liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) method for the measurement of PBG in 1 mL of urine, using 5-(aminoethyl)-4-(carboxymethyl) 1H-2,4-[13C]pyrolle-3-propanoic acid ([2,4-13C]PBG; 2.75 μg) as internal standard. After solid-phase extraction, LC-MS/MS analysis was performed in the selected-reaction monitoring (SRM) mode. PBG and [2,4-13C]PBG were monitored through their own precursor and product ion settings (m/z 227 to 210 and m/z 229 to 212, respectively). The retention time of PBG and [2,4-13C]PBG was 1.0 min in a 2.3-min analysis.

Results: Daily calibrations (n = 6) between 0.1 and 2.0 mg/L were linear and reproducible. Inter- and intraassay CVs were 3.2–3.5% and 2.6–3.1%, respectively, at mean concentrations of 0.24, 1.18, and 2.15 mg/L. The regression equation for the comparison between an anion-exchange column method (y) and the LC-MS/MS method (x) was: y = 0.84x + 0.74 (Sy|x = 5.8 mg/24 h; r = 0.85; n = 100). In 47 volunteers, PBG excretion was 0.02–0.42 mg/24 h, lower than reported reference intervals (up to 2.0 mg/24 h) based on colorimetric methods. In 85 samples with PBG ≤0.5 by LC-MS/MS, 8 (9.4%) had values ≥2.0 mg/24 h by the anion-exchange method (mean ± SD, 4.3 ± 1.8 mg/24 h). In 11 patients with confirmed diagnoses of acute porphyria and increased PBG by LC-MS/MS, 2 had values within the reported reference intervals by a quantitative anion-exchange method.

Conclusions: The quantitative LC-MS/MS method for PBG measurement exhibits greater analytical specificity and improved clinical sensitivity and specificity than currently available methods.

Pseudoporphyria: a clinical and biochemical study of 20 patients

OBJECTIVE

To describe the clinical and laboratory findings in patients with pseudoporphyria.

PATIENTS AND METHODS

This retrospective review identified 261 patients with either porphyrin metabolism abnormalities or pseudoporphyria who were seen at the Mayo Clinic in Rochester, Minn, between 1992 and 1996. All patients with documented porphyria cutanea tarda (PCT), noncutaneous porphyrias, or variegate porphyria were excluded.

RESULTS

Twenty patients had active cutaneous lesions resembling PCT with no diagnostic laboratory abnormalities. The major presenting clinical features were blistering in 19 patients (95%), scarring in 14 (70%), photosensitivity in 13 (65%), skin fragility in 13 (65%), and milia in 8 (40%). Histologically, of 17 patients tested, 12 (71%) had classic findings of subepidermal separation with festooning of dermal papillae. None of the 11 patients tested had hepatitis B or C. In all 20 patients, porphyrin profiles were nondiagnostic. Of 16 patients for whom follow-up was available, 11 reported persistent symptoms for a mean of 2.5 years after evaluation. Five patients were free of symptoms 1 week to 6 months after discontinuation of the presumed offending agent.

CONCLUSION

Pseudoporphyria mimics the cutaneous symptoms of PCT in the setting of normal or near-normal porphyrin levels in the serum, urine, or stool. Despite efforts to discontinue an offending medication, symptoms may persist indefinitely.

Cutaneous deposition diseases. Part I

The cutaneous deposition disorders are a group of unrelated conditions characterized by the presence of either endogenous or exogenous substances within the dermis or the subcutis. Part I of this two-part series will focus on metabolic processes involved in the endogenous deposition in the various forms of amyloidosis, porphyria, colloid milium, and lipoid proteinosis. We will also review the clinical, histologic, biochemical, and ultrastructural findings relevant to each disorder. Basic mechanisms of pathogenesis, diagnostic modalities, and treatment options are also discussed.

Cimetidine in the treatment of acute intermittent porphyria

Treatment options for AIP remain limited. Although no single therapy has been proven superior in clinical trials, intravenous hemin appears to be more effective than increased carbohydrate intake, and remains the treatment of choice. At usual dosages the average wholesale price of hemin is $120-475 per day (for a patient weighing 70 kg), compared with $2.50 per day for cimetidine. Cimetidine may offer a more cost-effective and easily administered alternative to hemin therapy. The optimal dosage and duration of treatment with cimetidine have not been established and are likely to be patient-specific. Oral doses of 800 mg/d have been used. In addition to its potential for treatment, cimetidine may also have a role in prophylaxis of acute episodes by maintaining a baseline suppression of ALA synthase activity. Until well-designed, controlled clinical trials demonstrate its efficacy and compare it with other treatment options, cimetidine should be reserved for use only after standard treatment modalities have failed.