Porphyric neuropathy

Porphyria

Porphyria are a group of metabolic disorders arising from a defect in the heme biosynthetic pathway.  Clnical presentation is diverse and neuropathies, and an acute intermittent porphyria (AIP).   AIP is an autosomal dominant disease due to deficiency of hydroxmethylbilane synthase (encoded by HMBS gene).  Most, if not at all, peripheral neuropathy is described have concomitant involvement of the large nerve fibers, suggesting that he does not appear SFN.  However, autonomic neuropathy was responsible for variety of symptoms during the acute attack and the majority of patients with AIP.  Manifest with autonomic dysfunction without large fiber peripheral neuropathy or focal CNS impairment.

Clinical features:  The acute neurological features are similar, however, a photosensitive rash is seen with HCP and VP but not seen in AIP.  Attacks of porphyria can be triggered by certain drugs (usually those metabolized by the P450 system), hormonal changes (pregnancy, and luteal phase of the menstrual cycle), and dietary restrictions. 

An acute attack of porphyria is often heralded by acute abdominal pain.  Later patients may develop agitation, hallucinations, or seizures.  Several day later, back and leg pain followed by weakness can occur and may mimic GBS.  Motor involvement is usually asymmetric, proximal, or distal and affects arms or leg preferentially.  CN are also affected, leading to facial weakness and dysphagia. Sensory impairment may be difficult to determine if the patient is encephalopathic.  Muscle stretch reflexes are often reduced.  Autonomic dysfunction manifested by signs of sympathetic overactivity (pupillary dilatation, tachycardia, and HTN) is common.  Constipation, urinary retention, and incontinence can also be seen.  Recovery is usually good, provided treatment is instituted rapidly to prevent excessive amounts of axonal damage. 

Laboratory features: