Systemic Lupus Erythematosus and Hereditary Coproporphyria: Two Different Entities Diagnosed by WES in the Same Patient.

Background: Hereditary coproporphyria (HCP) is a rare autosomal dominant disorder caused by a partial deficiency of coproporphyrinogen III oxidase (CPOX), and systemic lupus erythematosus (SLE) is an autoimmune disease with a strong genetic predisposition. SLC7A7 (solute carrier family 7 member 7) may be associated with monogenic lupus disease; however, only 2 cases of concomitant HCP and SLE have been reported. Methods: We report a 30-year-old woman with a six-year history of SLE presenting with abdominal pain, vomiting, dysuria, tachycardia, and hyponatremia. Whole exome sequencing (WES) and Sanger sequencing were carried out for the proband and members of her pedigree to detect the genetic background. The Gene Expression Omnibus (GEO) database was used to search the related gene expression profiles. Differentially expressed genes (DEGs) were identified using GEO2R. Result: A novel heterozygous splicing mutation of CPOX (NM_000097): c.700+2 T > C (intron 2) was detected by WES in the proband, and it was considered likely pathogenic (PSV1+PM2). Sanger sequencing verified the heterozygous mutation of CPOX in the proband, although it was not detected in her father. WES also identified 62 other gene variants, especially two heterozygous variants in SLC7A7 (NM_001126106): c.250G > A (p. V84I) and c.625+1G > A (splicing). DEGs were detected from GSE51997, and the expression of CPOX was downregulated in SLE patients compared with normal controls (adj. P = 0.0071, logFC = -1.0975). Conclusion: This study presents the first reported case of SLE coexisting with HCP in China; moreover, a novel splicing mutation of CPOX, i.e., c.700+2 T > C (intron 2), and two heterozygous mutations of SLC7A7 were reported. The simultaneous mutations of CPOX and SLC7A7 may explain the etiopathogenetic connections of HCP and SLE.

[The cutaneous porphyrias]. / Porphyries cutanées.

The porphyrias are a group of metabolic disorders resulting from an innate abnormality in haem biosynthesis, and the clinical settings of which vary according to the genetic enzyme abnormality in question. These are genetic disorders with autosomal dominant or recessive inheritance of varying penetrance, and whose clinical expression differs according to the preferential location of haem precursors. Different classifications have been proposed according to genetic inheritance, the enzyme anomaly at issue, and clinical expression. The clinical classification distinguishes between acute porphyria (acute intermittent porphyria, porphyria variegata, hereditary coproporphyria), bullous cutaneous porphyrias (porphyria cutanea tarda, porphyria variegata and hereditary coproporphyria), painful photosensitive acute cutaneous porphyrias (erythropoietic protoporphyria and X-linked dominant protoporphyria), and rare recessive porphyrias (congenital erythropoietic porphyria, Doss porphyria, hepatoerythropoietic porphyria and harderoporphyria). Treatment depends on the clinical expression of the disorder.

A case of hereditary coproporphyria with posterior reversible encephalopathy and novel coproporphyrinogen oxidase gene mutation c.863T>G (p.Leu288Trp).

A 21-year-old female had recurrent presentations to the emergency department with myalgia, vomiting, abdominal pain and subsequently developed generalized seizures. She was volume depleted with a plasma sodium of 125 mmol/L (reference interval: 135-145) and she had fluctuating hypertension. Acute porphyria was suspected and confirmed with raised urine porphobilinogen/creatinine ratio of 12:4 µmol/mmoL (reference interval < 1:5) and she was treated with intravenous haem arginate. Urinary porphyrin/creatinine ratio was 673 nmol/mmoL (reference interval <35) and faecal porphyrins 2430 µmol/kg dry weight (reference interval: <200) were markedly elevated, with raised faecal CIII:CI ratio, consistent with acute coproporphyria. Diagnosis was confirmed by the demonstration of a novel missense variant in the coproporphyrinogen oxidase gene c.863T > G (p.Leu288Trp) predicted to be deleterious and which segregated with three other affected family members. Although CT head was normal, magnetic resonance imaging scan revealed symmetrical signal abnormalities and swelling in the parietal and occipital lobes consistent with posterior reversible encephalopathy. Over several days, her seizures ceased and sodium and blood pressure normalized. The aetiology of the acute porphyric attack was likely multifactorial with contributions from a recent viral illness and caloric deprivation. No drug precipitant was identified. We postulate that untreated hypertension played a key role in the development of posterior reversible encephalopathy. Early clinical suspicion and urine porphobilinogen testing are the key components in preventing morbidity and mortality in acute porphyrias.

A mouse model of hereditary coproporphyria identified in an ENU mutagenesis screen.

A genome-wide ethyl-N-nitrosourea (ENU) mutagenesis screen in mice was performed to identify novel regulators of erythropoiesis. Here, we describe a mouse line, RBC16, which harbours a dominantly inherited mutation in the Cpox gene, responsible for production of the haem biosynthesis enzyme, coproporphyrinogen III oxidase (CPOX). A premature stop codon in place of a tryptophan at amino acid 373 results in reduced mRNA expression and diminished protein levels, yielding a microcytic red blood cell phenotype in heterozygous mice. Urinary and faecal porphyrins in female RBC16 heterozygotes were significantly elevated compared with that of wild-type littermates, particularly coproporphyrinogen III, whereas males were biochemically normal. Attempts to induce acute porphyric crises were made using fasting and phenobarbital treatment on females. While fasting had no biochemical effect on RBC16 mice, phenobarbital caused significant elevation of faecal coproporphyrinogen III in heterozygous mice. This is the first known investigation of a mutagenesis mouse model with genetic and biochemical parallels to hereditary coproporphyria.

Liver failure after Hydroxycut™ use in a patient with undiagnosed hereditary coproporphyria.

We report the case of a young male presenting with cholestatic liver failure. After an extensive workup, the etiology of the liver failure was determined to be due to hereditary coprophorphyria (HCP). The inciting event was the use of Hydroxycut™, an over-the-counter supplement to promote weight loss that has been reported to cause oxidative liver injury in vulnerable populations. Although HCP is a rare cause of cholestatic liver failure, it is treatable if diagnosed correctly and in a timely manner. In this clinical vignette, we discuss a case that highlights the genetic susceptibility to disease that can be unmasked by environmental exposures. We also review the relevant literature on Hydroxycut™ and how it can affect hepatic function.

Acute porphyrias in the USA: features of 108 subjects from porphyrias consortium.

BACKGROUND: Recent descriptions of the clinical and laboratory features of subjects with acute porphyrias in the US are lacking. Our aim was to describe clinical, biochemical, and genetic features of 108 subjects. METHODS: Between September 2010 and December 2012, 108 subjects with acute porphyrias (90 acute intermittent porphyrias, 9 hereditary coproporphyrias, 9 variegate porphyrias) were enrolled into an observational study. Genetic testing was performed at a central genetic testing laboratory and clinical information entered into a central database. Selected features were compared with data for adults in the US. RESULTS: Most subjects (88/108, 81%) were female, with self-reported onset of symptoms in the second through fourth decades of life. The most common symptom was abdominal pain. Appendectomies and cholecystectomies were common before a diagnosis of porphyria. The diagnosis was delayed by a mean of 15 years. Anxiety and depression were common, and 18% complained of chronic symptoms, especially neuropathic and other pains. The incidences of systemic arterial hypertension, chronic kidney disease, seizure disorders, and psychiatric conditions were markedly increased. Mutations of the known causative genes were found in 102/105 of those tested, with novel mutations being found in 37, including in 7/8 subjects with hereditary coproporphyria. Therapy with intravenous hematin was the most effective therapy both for treatment of acute attacks and for prevention of recurrent attacks. CONCLUSIONS: Acute porphyrias often remain undiagnosed for more than a decade after first symptoms develop. Intravenous hematin is the treatment of choice, both for treatment of acute attacks and for prevention of recurrent attacks.

Cutaneous porphyrias part I: epidemiology, pathogenesis, presentation, diagnosis, and histopathology.

The porphyrias are a group of disorders characterized by defects in the heme biosynthesis pathway. Many present with skin findings including photosensitivity, bullae, hypertrichosis, and scarring. Systemic symptoms may include abdominal pain, neuropsychiatric changes, anemia, and liver disease. With advances in DNA analysis, researchers are discovering the underlying genetic causes of the porphyrias, enabling family members to be tested for genetic mutations. Here we present a comprehensive review of porphyria focusing on those with cutaneous manifestations. In Part I, we have included the epidemiology, pathogenesis, presentation, diagnosis, and histopathology. Treatment and management options will be discussed in Part II.

The enzyme engineering of mutant homodimer and heterodimer of coproporphyinogen oxidase contributes to new insight into hereditary coproporphyria and harderoporphyria.

Hereditary coproporphyria (HCP) is an autosomal dominant-inherited disease of haem biosynthesis caused by partial deficiency of the enzyme coproporphyrinogen oxidase (CPOX). Patients with HCP show <50% of normal activity and those with the rare autosomal recessive harderoporphyria accumulate harderoporphyrinogen, an intermediate porphyrin of the CPOX reaction. To clarify the relationship of the low enzyme activity with these diseases, we expressed mutant CPOX carrying His-tag from these porphyria patients and co-expressed mutant CPOX carrying His-tag and normal CPOX carrying HA-tag in a tandem fashion in Escherichia coli. Purification of the His-tag-containing enzyme revealed that the His-enzyme forms a heterodimer in association with the HA-enzyme, and analysis using a cross-link reagent confirmed that the enzyme is a dimer (∼70 kDa). Then, we expressed homo- and heterodimers composed of the wild-type (wt) and engineered mutants of the enzyme or mutants from HCP patients. The monomer form of mutated CPOX did not show any activity and homodimeric enzymes derived from HCP mutant showed low activity (<20% of the control). Some mutations of amino acids 401-404 were associated with marked accumulation of harderoporphyrinogen, with a decrease in the production of protoporphyrinogen, whereas K404E derived from patients with harderoporphyria produced less harderoporphyrinogen. The heterodimers with wt and mutated subunits from HCP patients showed low protoporphyrinogen producing activity. These results show that the substitution of amino acids from R401 to K404 results in extremely low enzyme activity with either mutant homodimer or heterodimers containing normal and mutated subunits and can be linked to HCP disease.

Co-existence of hereditary coproporphyria and porphyria cutanea tarda: The importance of genetic testing.

The porphyrias are a group of inherited disorders that result in defects in the enzymes of the haem biosynthetic pathway, causing photosensitive bullous skin eruptions or abdominal and neurological attacks. Enzymatic defects result in specific porphyrin excretory patterns that are diagnosed biochemically and can be confirmed by genetic testing. Defects in the coproporphyrinogen oxidase (CPOX) enzyme result in the autosomal dominant hereditary coproporphyria. Multiple mutations have been identified in the CPOX gene and incomplete penetrance is noted. Latent carriers without clinical evidence of disease are at risk of life-threatening attacks. Porphyria cutanea tarda may be inherited, but is more commonly acquired. Occasionally two forms of porphyria may co-exist. The importance of genetic testing is discussed.

Identification of an AluY-mediated deletion of exon 5 in the CPOX gene by MLPA analysis in patients with hereditary coproporphyria.

Hereditary coproporphyria (HCP) is an autosomal dominantly inherited hepatic porphyria, caused by a mutation in the coproporphyrinogen oxidase (CPOX) gene. The genetic defect leads to a partial defect of CPOX, the sixth enzyme involved in haem biosynthesis. Affected individuals can develop acute life-threatening attacks of neurovisceral symptoms and/or more rarely cutaneous symptoms such as skin fragility and blistering. The identification of the genetic defect in HCP families is of crucial importance to detect the carrier status which allows counselling to prevent possible triggering factors, e.g. certain drugs, alcohol, or fasting. In a total of nine Swedish HCP families, routine gene sequence analysis had identified a causative mutation in only five. In the present study, using an in-house developed synthetic probe set for multiplex ligation-dependent probe amplification (MLPA) analysis, we detected a deletion of the fifth exon in the CPOX gene in the remaining four families. The deletion is 3381 bp in size and has originated by an Alu-mediated mechanism. This finding emphasizes the usefulness of MLPA analysis as a complement to gene sequencing for comprehensive genetic diagnostics in HCP patients.

Digenic inheritance of mutations in the coproporphyrinogen oxidase and protoporphyrinogen oxidase genes in a unique type of porphyria.

The simultaneous dysfunction of two enzymes within the heme biosynthetic pathway in a single patient is rare. Not more than 15 cases have been reported. A woman with a transient episode of severe photosensitivity showed a biochemical porphyrin profile suggestive of hereditary coproporphyria (HCP), whereas some of her relatives had a profile that was suggestive of variegate porphyria (VP). HCP and VP result from a partial enzymatic deficiency of coproporphyrinogen oxidase (CPOX) and protoporphyrinogen oxidase (PPOX), respectively. DNA analysis in the index patient revealed mutations in both the CPOX and PPOX genes, designated as c.557-15C>G and c.1289dupT, respectively. The CPOX mutation leads to a cryptic splice site resulting in retention of 14 nucleotides from intron 1 in the mRNA transcript. Both mutations encode null alleles and were associated with nonsense-mediated mRNA decay. Given the digenic inheritance of these null mutations, coupled with the fact that both HCP and VP can manifest with life-threatening acute neurovisceral attacks, the unusual aspect of this case is a relatively mild clinical phenotype restricted to dermal photosensitivity.

Harderoporphyria due to homozygosity for coproporphyrinogen oxidase missense mutation H327R.

Hereditary coproporphyria (HCP) is an autosomal dominant acute hepatic porphyria due to the half-normal activity of the heme biosynthetic enzyme, coproporphyrinogen oxidase (CPOX). The enzyme catalyzes the step-wise oxidative decarboxylation of the heme precursor, coproporphyrinogen III, to protoporphyrinogen IX via a tricarboxylic intermediate, harderoporphyrinogen. In autosomal dominant HCP, the deficient enzymatic activity results primarily in the accumulation of coproporphyrin III. To date, only a few homozygous HCP patients have been described, most having Harderoporphyria, a rare variant due to specific CPOX mutations that alter enzyme residues D400-K404, most patients described to date having at least one K404E allele. Here, we describe a Turkish male infant, the product of a consanguineous union, who presented with the Harderoporphyria phenotype including neonatal hyperbilirubinemia, hemolytic anemia, hepatosplenomegaly, and skin lesions when exposed to UV light. He was homoallelic for the CPOX missense mutation, c.980A>G (p.H327R), and had massively increased urinary uroporphyrins I and III (9,250 and 2,910 µM, respectively) and coproporphyrins I and III (895 and 19,400 µM, respectively). The patient expired at 5 months of age from an apparent acute neurologic porphyric attack. Structural studies predicted that p.H327R interacts with residue W399 in the CPOX active site, thereby accounting for the Harderoporphyria phenotype.

The acute hepatic porphyrias: current status and future challenges.

The porphyrias are predominantly inherited metabolic disorders, which result from a specific deficiency of one of the eight enzymes along the pathway of haem biosynthesis. Historically, they have been classified into hepatic and erythropoietic forms, based on the primary site of expression of the prevailing dysfunctional enzyme. From a clinical point of view, however, it is more convenient to subdivide them into acute and non-acute porphyrias, thereby primarily considering the potential occurrence of life-threatening acute neurovisceral attacks. Unrecognised or untreated, such an acute porphyric attack is associated with a significant mortality of up to 10%. The acute hepatic porphyrias comprise acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and δ-aminolevulinic acid dehydratase deficiency porphyria. Making a precise diagnosis may be difficult because the different types of porphyrias may show overlapping clinical and biochemical characteristics. To date, the therapeutic possibilities are limited and mainly symptomatic. In this overview we report on what is currently known about pathogenesis, clinic, diagnostics, and therapy of the acute hepatic porphyrias. We further point out actual and future challenges in the management of these diseases.

Four novel mutations of the coproporphyrinogen III oxidase gene.

Here we report the characterization of four novel mutations and a previously described one of the coproporphyrinogen III oxidase (CPO) gene in five Italian patients affected by Hereditary Coproporphyria (HCP). Three of the novel genetic variants are missense mutations (p.Gly242Cys; p.Leu398Pro; p.Ser245Phe) and one is a frameshift mutation (p.Gly188TrpfsX45).