Porphyria Educational Services
PORPHYRIA EDUCATIONAL SERVICES BULLETIN
Vol. 2 No. 17 April 23, 2000
FOCUS: Delta-Aminolevulinic Acid Dehydratas Deficiency [ALA-D]
Porphyria
ALA-D porphyria is an autosomal recessive disorder. The ALA-D is
now the
rarest porphyria. ALA-D results from a deficiency of ALA
dehydratase in the heme
pathway.
There are several different mutations in the gene for ALA
dehydratase
that have been charted in non-related patients. The ALA-D disease
was
first described in Germany . However the disease probably occurs
in
all countries.
The ALA-D Icauses neurologic symptoms and sometimes anemia.
ALA-D's symptomology resembles those of the acute porphyrias but
can also include hemolysis and anemia.
Symptoms of ALA-D may begin in infancy or adulthood. In ALA-D the
urinary ALA
and coproporphyrin III and erythrocyte zinc protoporphyrin are
markedly increased.
In ALA-D and other disorders in which ALA accumulates, excess ALA
may be
metabolized to coproporphyrin III in tissues other than the
tissue of origin of the excess ALA.
In ALA-D the fecal porphyrin excretion is normal or marginally
elevated.
Patients with ALA-dehydratase-deficient porphyria demonstrate
little activity of ALA
dehydratase in erythrocytes or in nonerythroid cells. Parents of
an ALA-D
porphyric show about 50% enzyme activity.
The diagnosis of ALA-D is made by finding an excess of ALA and
coproporphyrin
in urine and a deficiency of ALA dehydratase in erythrocytes. One
thing that is important
to remember is that other causes of this enzyme deficiency, such
as lead poisoning
and tyrosinemia, must be excluded.
These conditions can also manifest with symptoms such as
abdominal pain, ileus, and motor neuropathy that are strikingly
similar to
those of the acute porphyrias.