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Porphyria cutanea tarda

Porphyria cutanea tarda is the most common type of porphyria. The disorder results from low levels of the enzyme responsible for the fifth step in heme production. Heme is a vital molecule for all of the body's organs. It is a component of hemoglobin, the molecule that carries oxygen in the blood. Porphyria cutanea tarda is a subtype of porphyria. more...

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When signs and symptoms occur, they usually begin in adulthood and result from the skin becoming overly sensitive to sunlight. Areas of skin exposed to the sun develop severe blistering, scarring, changes in pigmentation, and increased hair growth. Exposed skin becomes fragile and is easily damaged. People with porphyria cutanea tarda also have increased iron levels in the liver. They face a higher risk of developing abnormal liver function and liver cancer. The signs and symptoms of this condition are triggered by nongenetic factors such as alcohol abuse, excess iron, certain hormones, and viral infections.

Epidemiology

This type of porphyria occurs in an estimated 1 in 25,000 people, including both inherited and sporadic (noninherited) cases. An estimated 80 % of porphyria cutanea tarda cases are sporadic. The exact frequency is not clear because many people with the condition never experience symptoms.

Genetics

Inherited mutations in the UROD gene cause about 20 % of cases. (The other 80 % of cases do not have mutations in UROD, and are classified as sporadic.) UROD makes an enzyme called uroporphyrinogen decarboxylase, which is critical to the chemical process that leads to heme production. The activity of this enzyme is usually reduced by 50 % in all tissues in people with the inherited form of the condition.

Nongenetic factors such as alcohol abuse, excess iron, and others listed above can increase the demand for heme and the enzymes required to make heme. The combination of this increased demand and reduced activity of uroporphyrinogen decarboxylase disrupts heme production and allows byproducts of the process to accumulate in the body, triggering the signs and symptoms of porphyria cutanea tarda.

The HFE gene makes a protein that helps cells regulate the absorption of iron from the digestive tract and into the cells of the body. Certain mutations in the HFE gene cause hemochromatosis (an iron overload disorder). People who have these mutations are also at an increased risk of developing porphyria cutanea tarda.

In the 20% of cases where porphyria cutanea tarda is inherited, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene is sufficient to decrease enzyme activity and cause the signs and symptoms of the disorder.

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Vesiculobullous disease
From Journal of Family Practice, 4/1/05 by Gary N. Fox

To the Editor:

In the journal's Photo Rounds, Drs Sauret, Yale, and Ahiarah present a case of vesiculobullous disease ("Rupturing bullae not responding to antibiotics," J Fam Pract 2004; 53112]:981-983). We would like to offer additional comment we believe pertinent to family physicians.

In obtaining a biopsy in patients with vesiculobullous eruptions, there are several important factors to be considered compared with most other dermatoses. (1) First, biopsy specimens for immunofluorescence examinations cannot be submitted in the usual specimen preservatives. Instead, they need to be submitted in special transport media for immunofluorescence (typically Michel's medium) or as "fresh" specimens. For the latter, the physician uses a sterile container lined with saline-moistened gauze, into which the biopsy specimen is sealed and then transported to the pathologist "stat" or frozen until picked up. Perilesional skin is best for direct immunofluorescence testing of bullous diseases. Second, an additional specimen should be sent for routine histology. This can be accomplished either by doing two biopsies or by sectioning 1 sufficiently large specimen. Third, lesional skin is required for pathologic evaluation. However, with vesiculobullous eruptions, including perilesional skin allows a point of adherence for the roof of the lesion to the remainder of the lesion. The fourth difference is that a sample of the patient's serum is required for indirect immunofluorescence. Last, because of these logistics, it may be helpful to communicate with the dermatopathologist when biopsying lesions where immunofluorescence studies are considered. Although similar to lesion sampling in other dermopathies, but of critical importance in vesiculobullous disease, choice of lesions for sampling is important. The ideal lesions are fresh (less than 24-48 hours old), intact, and nonexcoriated vesiculobullae, with normal or erythematous perilesional skin for inclusion in the biopsy field.

In teaching residents about vesiculobullous disease, our simplified approach is to state that all primary care physicians should be facile with 3 categories. The first is infections--both viral, such as herpes simplex, varicella-zoster, and Enteroviral (including Coxsackie) infections--and bacterial, including bullous impetigo and staphylococcal scalded skin syndrome. The second category is acute eczematous tissue reactions including allergic contact dermatitis. The third is exogenous trauma, such as thermal burns, bug bites, and friction-induced lesions. The fourth category includes the less common inflammatory bullous diseases and may be within the purview of interested primary care physicians but is always fair game for referral--sometimes urgently. A partial list includes pemphigus, bullous pemphigoid, porphyria cutanea tarda, epidermolysis bullosa, erythema multiforme, drug eruptions, dermatitis herpetiformis and toxic epidermal necrolysis. Division into these categories may be helpful in delineating further workup, including culture and biopsy for pathology and immunofluorescence.

REFERENCE

(1.) Vesicular and bullous diseases (Chapter 16). In: Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. New York, NY: Mosby, Inc; 2004:547-554.

FAST TRACK Primary care physicians should be facile with 3 categories when diagnosing vesiculobullous disease

Gary N. Fox, MD Medical College of Ohio; Mercy Health Partners Family Practice Residency, Toledo

Gregory L. Swartz, DO Ohio University; Mercy Health Partners Family Practice Residency, Toledo

Darius R. Mehregan Wayne State University, Detroit MI, and Clinical Associate Professor of Pathology, Medical College of Ohio, Toledo

COPYRIGHT 2005 Dowden Health Media, Inc.
COPYRIGHT 2005 Gale Group

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