Posterior reversible encephalopathy in porphyria
11 years old female, diagnosed with acute intermittent porphyria 5 years ago, came with complains of fever and altered sensorium since 1 day. Spot urine Porphobilinogen and delta-Aminolevulinic Acid levels were 3.91 mg/dl and 3.10 mg/dl respectively.
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MRI brain axial sections showing bilateral parietooccipital hyperintense signals involving cortical and subcortical areas on FLAIR, T1 and T2 images with no restriction on diffusion weighted images. No blooming present on GRE images. Mild contrast enhancement is noted on post contrast images in the involved cortical and subcortical areas in bilateral parietooccipital regions .
Porphyrias are rare inherited metabolic disorders of heme biosynthesis that lead to pathological accumulation of various porphyrins and their precursors. The inheritance is autosomal dominant. Neurological manifestations of acute intermittent porphyria are varied with involvement of central, peripheral and autonomic nervous systems. The incidence of neurological manifestations in symptomatic patients is very low ( 5-17%).
PRES is a common imaging abnormality seen in acute intermittent porphyria. PRES presents with sudden onset of headache, seizures, altered mental status and visual disturbances which is most commonly associated with acute hypertension, eclampsia and immunosuppressive agents. Posterior reversible encephalopathy is characterized by reversible vasogenic subcortical edema without infarction. Although typically parieto occipital regions are involved, atypical presentations are not infrequent.
The etiology of PRES in acute intermittent porphyria is proposed to be due to disruption of blood brain barrier and blood-nerve barrier caused by accumulation of porphyrin precursors.
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