[Acute intermittent porphyria and inappropriate ADH syndrome]

Recurrent Seizures in an Adolescent Female-A Daunting Puzzle

Acute porphyrias are metabolic disorders resulting from deficiency of a specific enzyme involved in heme biosynthetic pathway. These deficiencies also affect normal renal physiology, as kidneys are also involved in heme synthesis. Sometimes, this could even lead to end stage renal disease. Acute Intermittent Porphyria, an autosomal dominant disorder arising from half-normal activity of hydroxymethylbilane synthase, is characterized by occurrence of vague neurovisceral attacks (abdominal pain, nausea, vomiting, constipation and neuropsychiatric symptoms), with urinary excretion of porphyrin precursors, such as 5-Amino-levulinic acid (ALA) and Porphobilinogen (PBG). Acute attacks are triggered by dehydration, diarrhea, steroids, low calorie diets. Treatment includes avoidance of precipitating factors, adequate hydration, high carbohydrate diet and heme replacement. Here, we present an adolescent female who had presented with recurrent abdominal pain, dyselectrolyemia with associated seizures, was diagnosed with Acute Intermittent Porphyria and recovered well with symptomatic management.

Novel mutation of PPOX gene in a patient with abdominal pain and syndrome of inappropriate antidiuresis

PURPOSE

Acute porphyrias are metabolic disorders of heme biosynthesis characterized by acute life-threatening attacks. The diagnosis is often missed since clinical presentation is aspecific mimicking other medical and surgical conditions. Variegate porphyria (VP) is an autosomal dominant inherited disease with incomplete penetrance due to decreased activity of the Protoporphyrinogen Oxydase (PPOX) gene; most VP mutations are family specific. We report the case of a 40 year-old woman who presented many times to the emergency department complaining of unexplained abdominal pain and laboratory investigations showed repeatedly hyponatremia. Syndrome of inappropriate antidiuresis (SIAD) was confirmed and measurement of urine porphobilinogen and delta-aminolevulinic acid disclosed the diagnosis of acute porphyria. The genetic analysis of PPOX gene was performed.

METHODS

The entire coding sequence and exon/intron boundaries of PPOX gene were amplified in 5 different Polymerase Chain Reaction (PCR) fragments. In silico prediction of the pathogenicity of the mutation was determined by using different tools, Polyphen2, SNPs&GO, SNPs3D.

RESULTS

The genetic analysis of PPOX gene revealed a novel missense variant c.1376 G > A (p.Cys459Tyr) in heterozygous state. The same variant was later found in one of her cousins with skin lesions and other three younger asymptomatic relatives. We provided evidence that this novel mutation is likely to be pathogenetic.

CONCLUSIONS

Our case highlights the importance of considering VP in the differential diagnosis of SIAD and underlines the role of genetic screening in the management of such patients. The finding of a novel mutation of PPOX gene in our index case has allowed to recognize an affected family.

Porphyria and kidney diseases

The kidneys, after the bone marrow and liver, are third in terms of the amounts of haem synthesized daily. Haem is incorporated into haemoproteins that are critical to renal physiology. In turn, disturbances in haem metabolism interfere with renal physiology and are tightly interrelated with kidney diseases. Acute intermittent porphyria causes kidney injury, whereas medical situations associated with end-stage renal disease, such as porphyrin accumulation, iron overload and hepatitis C, participate in the inhibition of uroporphyrinogen decarboxylase and predispose the individual to porphyria cutanea tarda. Even if some of these interactions have been known for a long time, the clinical situations associated with these interrelations have strikingly evolved over time with the advent of new therapeutic strategies for dialysis therapy and a better understanding of the pathophysiological mechanisms of porphyria-associated kidney disease. Physicians should be aware of these interactions. The aim of this review is to summarize the complex interactions between kidney physiology and pathology in the settings of porphyria and to emphasize their often-underestimated importance.