Penetrance

PPOX pathogenic variants that result in VP produce little or no functional enzyme; the approximately 50% of normal residual enzyme activity results primarily from the normal allele. Penetrance is low, but may be increased by factors that increase the demand for hepatic heme synthesis. Penetrance is likely influenced by modifying genes that remain to be identified.

Diagnostic Criteria

Suggestive Findings

Variegate porphyria (VP) should be suspected in individuals with the following clinical findings and initial laboratory findings.

Clinical findings

Source: GeneReviews — "Variegate Porphyria"

Management Guidelines

Evaluations Following Initial Diagnosis

To establish the extent of disease and to plan the management of an individual diagnosed with variegate porphyria (VP), the following clinical and laboratory evaluations (if not performed as part of the evaluation that led to the diagnosis) are recommended:

Surveillance Guidelines

Hepatocellular carcinoma may develop especially after age 50 years in patients with acute porphyrias and persistent elevations in porphobilinogen or porphyrins; liver imaging at six-month intervals beginning at age 50 years may detect early lesions .

Source: GeneReviews — "Variegate Porphyria"