Biochemical compared to molecular diagnosis in acute intermittent porphyria

Epidemiology of cutaneous porphyria in Israel: a nationwide cohort study

BACKGROUND

From a dermatologist's perspective, there are four major types of cutaneous porphyrias (CPs): porphyria cutanea tarda (PCT), erythropoietic protoporphyria (EPP), variegate porphyria (VP) and hereditary coproporphyria (HCP). Scarce data are available regarding the epidemiology of CPs.

OBJECTIVES

To describe the epidemiology of CPs in Israel, including distribution, incidence and prevalence rates of major types.

METHODS

This retrospective study includes all patients who were diagnosed with CPs between the years 1988-2018. It is based on data from Israel's National Service for the Biochemical Diagnoses of Porphyrias, and Israeli patients' nationwide electronic medical charts. Incidence and prevalence rates were calculated.

RESULTS

Of 173 patients with CPs diagnosed during a 30-year period, 65 (38%) had VP, 62 (36%) had PCT, 31 (18%) had HCP and 15 (9%) had EPP; with incidence rates of 0.29, 0.30, 0.17, 0.07, and prevalence rates of 6.3, 4.8, 2.9, 1.6, respectively, per million population. Characteristics of patients with PCT differed from those with other CPs with regard to lack of family history, older mean age at diagnosis [51 vs. 36 (VP), 35 (HCP) and 25 (EPP) years] and male predominance (81% vs. similar distribution). All patients with PCT were diagnosed at adulthood, while 20%, 19% and 15% of patients with VP, HCP and EPP, respectively, were diagnosed during childhood or adolescence.

CONCLUSIONS

Variegate porphyria and PCT were found to be the most prevalent in Israel; however, CPs might be underdiagnosed, thus dermatologists' awareness of these rare disorders is highly important.

A challenging diagnosis for potential fatal diseases: recommendations for diagnosing acute porphyrias

Acute porphyrias are a heterogeneous group of metabolic disorders resulting from a variable catalytic defect of four enzymes out of the eight involved in the haem biosynthesis pathway; they are rare and mostly inherited diseases, but in some circumstances, the metabolic disturbance may be acquired. Many different environmental factors or pathological conditions (such as drugs, calorie restriction, hormones, infections, or alcohol abuse) often play a key role in triggering the clinical exacerbation (acute porphyric attack) of these diseases that may often mimic many other more common acute medical and neuropsychiatric conditions and whose delayed diagnosis and treatment may be fatal. In order to obtain an accurate diagnosis of acute porphyria, the knowledge and the use of appropriate diagnostic tools are mandatory, even in order to provide as soon as possible the more effective treatment and to prevent the use of potentially unsafe drugs, which can severely precipitate these diseases, especially in the presence of life-threatening symptoms. In this paper, we provide some recommendations for the diagnostic steps of acute porphyrias by reviewing literature and referring to clinical experience of the board members of the Gruppo Italiano Porfiria (GrIP).

The acute porphyrias: a diagnostic and therapeutic challenge in internal and emergency medicine

The porphyrias are a heterogeneous group of metabolic diseases resulting from a variable catalytic defect of one of the eight enzymes involved in the heme biosynthesis pathway; they are mostly inherited diseases, but in some circumstances the metabolic disturbance may be acquired. The specific patterns of tissue overproduction (and hence accumulation and excretion) of toxic heme precursors, associated with each enzymatic deficiency, are responsible for the characteristic biochemical and clinical features of each of these diseases. Moreover, even in the presence of a specific inherited enzymatic defect, many different environmental factors (such as drugs, calorie restriction, hormones, sunlight exposition, infections, etc.) often play a key role in triggering the clinical expression of the various forms of porphyrias. The porphyrias are often misdiagnosed diseases, due their multiform clinical manifestations, able to mimic many other more common diseases. For this reason, many different specialists, such as surgeons, psychiatrists, gastroenterologists, neurologists, emergency physicians and dermatologists may be variably involved in the diagnostic process, especially for the forms presenting with acute and life-threatening clinical features. According to the clinical features, the porphyrias can be classified into neuropsychiatric (characterized by neurovisceral crises involving autonomic and central nervous system but also the liver and the kidney with possible consequences in terms of neurological, psychic, cardiac, respiratory, liver and kidney functions), dermatological (mostly presenting with cutaneous lesions due to photosensitivity), and mixed forms. From a strictly clinical point of view, porphyrias presenting with neurovisceral attacks are also referred as acute porphyrias: they are the object of the present review. An accurate diagnosis of acute porphyria requires knowledge and the use of correct diagnostic tools, and it is mandatory to provide a more appropriate therapeutic approach and prevent the use of potentially unsafe drugs, able to severely precipitate these diseases, especially in the presence of life-threatening symptoms. To date, availability of a relatively stable haem preparation (haem arginate) has significantly improved the treatment outcome of acute porphyric attacks, so the knowledge about the diagnosis and the management of these diseases may be relevant for physicians working in internal medicine, neurology and emergency units.