Wednesday, July 16, 2008

Porphyria pearls

taken from NEJM CPC 2008; 358;2813-2825

case (abbreviated severely). 57 year old woman was admitted with abdominal pain and weakness. She had just had bariatric surgery for obesity. MRI showed changes of posterior reversible leuokoencephalopathy syndrome (turns out it occurs in porphyria). She had had intermittent dark urine and tachycardia.

Patient developed numbness, weakness and tingling in lower extremities, fell while walking and had an episode of confusion and urinary incontinence. She quickly (within days) could not stand or sit independently, became incontinent of stool with numbness and tingling along her body. She had 4/5 strength throughout, with fatigueing and absent reflexes. Sensation was normal. CSF showed normal glucose, protein and no cells. EMG showed an acute motor neuropathy. Strength deteriorated to 0-3/5, worse in proximal than distal legs. There was no response to IVIG.

Pearls-- factors for porphyria in this case were recurrent severe abdominal pain, dark or reddish urine, arterial hypertension, tachycardia and constipation. The diagnostic test in 5-ALA and PBG in urine or serum. A rapid test is the PBG in urine (Hoesch or Watson-Schwartz reaction). Key is diagnose porphyria first then type it. (False positives in 5-ALA are lead posioning and hereditary tyrosinemia type I).

Most types are inherited but the most common type, porphyria cutanea tarda is acquired, associated with liver disease and iron overload. Of 4 types, any may present with neurovisceral presentation esp colicky abdominal pain, and hereditary coproporphyria and variegate porphyria can also present with cutaneous features. Attacks are likely precipitated by adverse effects of excess ALA which is structurally similar to GABA. Starvation, poor CH2O/ energy intake, drugs, alcohol, smoking, infections and stress can ppt. In this case the negative energy balance with surgery caused up regulation of hepatic ALA synthase 1, due to loss of CH2O repression of rate controlling enzyme for heme synthesis in the liver. Other "bad " drugs in this case were phenytoin, tramadol and bactrim. Sulfonamides and barbiturates are also "bad." So is progesterone (which is why postpubertal women are more susceptible). The treatment is i-v heme. It can prevent reversible axonal death. Prognosis is slow and incomplete recovery. Noted also in this case wwre blisters in sun exposed parts of the body. She had variegate porphyria.

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