Internal Medicine

0521779407-17 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 7:57

1194 Porphyria, Acute

■Early neurological findings (if present): extremity weakness, proxi-

mal muscles > distal.

■Late neurological presentation: flaccid paralysis and respiratory fail-

ure.

tests

■Urine porphobilinogen (PBG) and delta-aminolevulinic acid (ALA).

NOTE: this is not a “porphyrin screen”. For rapid PBG: Watson-

Schwartz test. In patients with acute symptoms, urine PBG is > 20

mg/24 h (normal < 2 mg) and often 60–200 mg/24 h. Normal PBG

in symptomatic patient excludes acute porphyria. Values in 2–20

mg/24 h range may identify a “silent” genetic carrier of the disease.

■CBC: mild leukocytosis; no left shift

■Serum electrolytes: hyponatriemia

■RBC uroporphyrinogen-1-synthetase (PBG deaminase): deficiency

is constant in genetic carriers of AIP. Not useful for diagnosing

acutely ill patients.

■Urine and fecal porphyrins: for identifying type of acute porphyria,

for genetic screening of family members

differential diagnosis

■If localized pain, fever and leukocytosis or rebound tenderness are

present, intra-abdominal inflammation (appendicitis, cholecystitis,

pancreatitis, vasculitis, volvulus, etc) must be excluded. Markedly

increased PBG otherwise is diagnostic.

■If urine shows predominant elevation of ALA with slightly elevated

or normal PBG, consider heavy metal intoxication, especially lead.

Check smear for basophilic stippling, and obtain blood lead level.

■Motor weakness can suggest Guillain-Barre syndrome. However,

in G-B, CSF has lymphocytes and elevated protein, which are not

present in porphyria.

■Elevation of urine coproporphyrin only (normal PBG) is non-

specific, occurring in diseases of the liver, bone marrow, nervous

system and others.

■Substantial elevation of uroporphyrin with normal PBG suggests

porphyria cutanea tarda (PCT), which is a cutaneous disease. Acute

pain attacks are not part of PCT.

management

■Eliminate possible porphyria-inducing drugs; discontinue all but

essential medications.

■Serial 24-hour urine collections for PBG