Case Report: Lack of Response to Givosiran in a Case of ALAD Porphyria

Profound hypotonia in an infant with δ-aminolevulinic acid dehydratase deficient porphyria

δ-Aminolevulinic acid (ALA) dehydratase (ALAD) deficient porphyria (ADP) is an extremely rare form of porphyria, with only eight documented cases. Herein, we report the second known case of ADP in the Western hemisphere and third case with infantile onset of symptoms. A male neonate presented on day three of life with profound hypotonia, pinpoint pupils, absent deep tendon reflexes, and anemia. Whole genome sequencing revealed two pathogenic missense ALAD variants, and subsequent biochemical testing confirmed a diagnosis of ADP. With supportive care and following erythrocyte transfusions for anemia, his hypotonia improved gradually. Neurological improvement following erythrocyte transfusion may have resulted from suppression of erythropoiesis and less overproduction of ALA and porphyrins by the marrow, which is an important consideration for long term management. This case highlights the importance of leveraging rapid whole genome sequencing for the diagnosis and minimization of devastating sequelae of exceptionally rare disorders, such as ADP.

Givosiran: a targeted treatment for acute intermittent porphyria

The acute hepatic porphyrias (AHPs) are a family of rare genetic diseases associated with attacks of abdominal pain, vomiting, weakness, neuropathy, and other neurovisceral symptoms. Pathogenic variants in 1 of 4 enzymes of heme synthesis are necessary for the development of AHP, and the onset of acute attacks also requires the induction of δ-aminolevulinic acid synthase 1 (ALAS1), the first and rate-limiting step of heme synthesis in the liver. Givosiran is an RNA interference medication that inhibits hepatic ALAS1 and was designed to treat AHP. In 2019 the US Food and Drug Administration approved givosiran for AHP based on positive results from a phase 3 clinical trial of 94 patients with AHP who demonstrated a marked improvement in AHP attacks and a substantial decrease in δ-aminolevulinic acid and porphobilinogen, the primary disease markers of AHP. A long-term follow-up study demonstrated continued improvement in AHP attack rates, biochemical measures of disease, and quality of life. Real-world studies have also confirmed these results. Common side effects include injection site reactions, hyperhomocysteinemia, and abnormalities of liver and renal biochemistries. This article reviews the studies that led to givosiran approval, discusses real-world clinical data, and highlights remaining questions in the treatment of AHP.

Exploring current and emerging therapies for porphyrias

Porphyrias are rare, mostly inherited disorders resulting from altered activity of specific enzymes in the haem synthesis pathway that lead to accumulation of pathway intermediates. Photocutaneous symptoms occur when excess amounts of photoreactive porphyrins circulate in the blood to the skin, whereas increases in potentially neurotoxic porphyrin precursors are associated with neurovisceral symptoms. Current therapies are suboptimal and their mechanisms are not well established. As described here, emerging therapies address underlying disease mechanisms by introducing a gene, RNA or other specific molecule with the potential to cure or slow progression of the disease. Recent progress in nanotechnology and nanoscience, particularly regarding particle design and formulation, is expanding disease targets. More secure and efficient drug delivery systems have extended our toolbox for transferring specific molecules, especially into hepatocytes, and led to proof-of-concept studies in animal models. Repurposing existing drugs as molecular chaperones or haem synthesis inhibitors is also promising. This review summarizes key examples of these emerging therapeutic approaches and their application for hepatic and erythropoietic porphyrias.

Acute hepatic porphyrias-A guide for hepatologists

The acute hepatic porphyrias (AHPs) are a group of rare, inherited disorders of the heme biosynthesis pathway, usually manifesting with attacks of acute abdominal pain and other neurovisceral symptoms, with or without cutaneous manifestations. AHPs are characterized by the accumulation of porphyrin precursors, porphobilinogen, and/or aminolevulinic acid, in the blood. The diagnosis is often missed or delayed due to both inadequate testing and the improper use of available laboratory tests. In this review, we describe the various clinical presentations of the 4 AHPs, elucidate the approach to diagnosis, and provide recommendations for immediate and long-term management. We also describe the different complications that can occur with long-standing AHP, including the development of HCC. The AHPs are very treatable conditions, with excellent outcomes if diagnosed and treated early. A high index of suspicion for the presence of these disorders, along with accurate testing and timely treatment, will help reduce the burden of disease and prevent irreversible complications in patients with AHP.

Update on the Porphyrias

The porphyrias are a group of rare diseases, each resulting from a defect in a different enzymatic step of the heme biosynthetic pathway. They can be broadly divided into two categories, hepatic and erythropoietic porphyrias, depending on the primary site of accumulation of heme intermediates. These disorders are multisystemic with variable symptoms that can be encountered by physicians in any specialty. Here, we review the porphyrias and describe their clinical presentation, diagnosis, and management. We discuss novel therapies that are approved or in development. Early diagnosis is key for the appropriate management and prevention of long-term complications in these rare disorders.