Some general information on this puzzling disease.
From: The Amercican Porphyria Foundation
Note--this is not meant as a means of diagnosis in any way; it is just
some basic information.
What Is Porphyria?
Porphyria is not a single disease but a group of at least eight disorders
that differ considerably from each other. A common feature in all
porphyrias is the accumulation in the body of "porphyrins" or "porphyrin
precursors". Although these are normal body chemicals, they normally do
not accumulate. Precisely which of these chemicals builds up depends upon
the type of porphyria.
The clinical manifestations of the different types of porphyria are not
the same. Forms of treatment also depend on the type of porphyria.
Therefore, it is difficult to make general statements that apply to all
The symptoms arise mostly from effects on the nervous system or the skin.
Effects on the nervous system occur in the acute porphyrias. Proper
diagnosis is often delayed because the symptoms are nonspecific. Skin
manifestations can include burning, blistering and scarring of sun-exposed
The terms "porphyrin" and "porphyria" are derived from the Greek word
"porphyrus" meaning purple. Urine from some porphyria patients may be
reddish in color due to the presence of excess porphyrins and related
substances, and the urine may darken after standing in the light.
How does one get Porphyria?
In each type of porphyria there is a deficiency of a specific "enzyme".
These enzymes are involved in the synthesis of heme, a substance important
to many body functions and found in largest amounts in the bone marrow,
red blood cells and the liver. Heme exists as hemoglobin in the bone
marrow and red blood cells but has other functions in other tissues such
as the liver. The type of porphyria present is determined by which enzyme
is deficient. These enzyme deficiencies are usually inherited.
Environmental factors, such as drugs, chemicals, diet and sun exposure
can, depending on the type of porphyria, greatly influenced the severity
The inherited porphyrias are either autosomal dominant (inherited from one
parent) or autosomal recessive (inherited from both parents). "Autosomal"
genes always occur in pairs, with one coming from each parent. Individuals
with an autosomal dominant form of porphyria have one abnormal gene paired
with a normal one, and half of their offspring (on the average) will
inherit the gene for the disease, while the other half will inherit the
normal gene. Some of those who inherit the abnormal gene will develop
symptoms. Individuals with an autosomal recessive type of porphyria have a
pair of abnormal genes, and each of their children will inherit one
abnormal gene for that disease, which will be paired with a normal gene
from the other parent, and there will be no symptoms. If two carriers of
the same abnormal recessive gene marry, approximately one fourth of their
children will inherit two abnormal genes, and these children will develop
symptoms of the disease. Because all porphyrias are uncommon, it is very
unlikely that more than one type will occur in the same family, or that
someone with one type of porphyria will go on to develop another.
What Treatment and Prevention are Available?
Treatment depends greatly on the type of porphyria and can be quite
successful. Preventive measures, which include avoidance of certain drugs
and alcohol, are also important in those who are identified as having
inherited porphyria, even if they have never had symptoms. Asymptomatic
carriers as well as patients who have symptoms should be educated about
Is Sunlight Always Harmful?
Sun sensitivity can occur in all but two types of porphyria. The degree of
sensitivity to sunlight varies considerably. Patients with sun sensitivity
have high levels of porphyrins in the blood plasma which, depending on the
type of porphyria, have originated from the liver or the bone marrow.
Ultraviolet light interacts with porphyrin in such a way as to damage skin
tissue. Some treatments may help patients tolerate sun exposure even
without lowering porphyrin levels. In some cases, treatment can lower
porphyrin levels, and sunlight can be tolerated.
Diagnostic Testing for Porphyrias
There are many laboratory tests available for porphyrias, and it is often
difficult to decide which should be chosen. Many of these tests are
expensive. The results are often difficult to interpret. The tests vary in
sensitivity and specificity. If a test is sensitive, it is unlikely to be
falsely negative (i.e. fail to diagnose porphyria in a patient who has the
disease). If a test is specific, it is unlikely to be falsely positive
(i.e. diagnose porphyria in a patient who does not have porphyria).
Certain tests are both sensitive and specific in patients who have
symptoms that are suggestive of porphyria. When abdominal and neurological
symptoms suggest an acute porphyria, the best screening tests are urinary
ALA and PBG. When there are cutaneous symptoms that suggest porphyria, the
best screening test is a plasma porphyrin determination. If one of these
screening tests is abnormal, more extensive testing, including urinary,
fecal and red blood cell porphyrins, are then indicated. Urinary, fecal,
and red blood cell porphyrin measurements are not very useful for initial
screening, because they lack either sensitivity or specificity and,
therefore, are often difficult to interpret. Measurement of heme
biosynthetic enzymes in red blood cells or lymphocytes is not appropriate
for screening, unless it is part of a family study that is done after
someone in the family is already known to have a particular enzyme
deficiency. It is advisable to have testing performed by a laboratory that
has expertise in the clinical aspects of porphyria and can provide a valid
interpretation of the test results.
If testing has been performed in laboratories other than porphyria
laboratories, consultation with a porphyria expert is advised before a
final diagnosis of acute porphyrias is accepted.