Uric acid metabolism in psoriasis

Hyperuricemia in Psoriatic Arthritis: Epidemiology, Pathophysiology, and Clinical Implications

Psoriatic arthritis (PsA) represents the articular component of the systemic psoriatic disease and the extra-cutaneous disorder most frequently found in patients with psoriasis. Besides the articular involvement, PsA is associated with several metabolic abnormalities such as insulin resistance, hypertension, diabetes and hyperuricemia. Uric acid is the final product of purine metabolism and the etiological substrate of gout. Accumulating evidence highlights the emerging role of hyperuricemia as a major cardiovascular risk factor. Moreover, different studies evaluated the interplay between hyperuricemia and psoriatic disease, suggesting that individuals affected by psoriasis or PsA might present higher serum levels of uric acid and that hyperuricemia might affect severity of clinical manifestations and degree of inflammation in PsA patients. In this review, we focus on the bidirectional relationship between uric acid and PsA, analyzing how uric acid may be involved in the pathogenesis of psoriasis/PsA and how clinical manifestations of PsA and inflammatory mediators are affected by uric acid concentrations. Finally, the effects of anti-rheumatic drugs on uric acid levels and the potential benefit of urate-lowering therapies on psoriasis and PsA were summarized.

Pathophysiology of Gout

Multiple interacting checkpoints are involved in the pathophysiology of gout. Hyperuricemia is the key risk factor for gout and is considered a prerequisite for monosodium urate (MSU) crystal formation. Urate underexcretion through renal and gut mechanisms is the major mechanism for hyperuricemia in most people. Multiple genetic, environmental, and metabolic factors are associated with serum urate and alter urate transport or synthesis. Urate supersaturation is the most important factor for MSU crystal formation, and other factors such as temperature, pH, and connective tissue components also play a role. The nucleotide-binding oligomerization domain leucine-rich repeats and pyrin domain-containing protein 3 inflammasome plays a pivotal role in the inflammatory response to MSU crystals, and interleukin 1β is the key cytokine mediating the inflammatory cascade. Variations in the regulatory mechanisms of this inflammatory response may affect an individual's susceptibility to developing gout. Tophus formation is the cardinal feature of advanced gout, and both MSU crystals and the inflammatory tissue component of the tophus contribute to the development of structural joint damage owing to gout. In this article, we review the pathophysiologic mechanisms of hyperuricemia, MSU crystal formation and the associated inflammatory response, tophus formation, and structural joint damage in gout.

At the crossroads of gout and psoriatic arthritis: "psout"

Psoriatic arthritis and gout are frequently encountered conditions sharing a number of common risk factors, which render their independent study difficult. Epidemiological studies have demonstrated a strong link between these diseases, suggesting the presence of underlying, intertwined pathophysiological mechanisms that currently remain unknown. Indeed, sodium urate crystals could play a pathogenic role in psoriasis and psoriatic arthritis. In daily practice, the distinction between psoriatic arthritis associated with hyperuricemia and a gouty arthropathy with psoriasis is complex. Several common pathogenic features suggest a more intricate relationship than their mere coexistence in the same patient. Thus, the concurrence of these two diseases should be seen as a novel overlap syndrome, at the boundary between inflammatory and metabolic rheumatism. The present update aims to clarify the determinants of the link and to define this new nosological entity. Its recognition could have therapeutic implications that appear essential for treatment optimization in a personalized setting.Key Points• What is already known about this subject? Psoriatic arthritis (PsA) and gout have strong interconnections, including comorbidities and pathophysiology. One must note that confounding clinical symptoms and radiological signs of PsA and gout are similar and difficult to differentiate in patients whose radiological lesions become too advanced to be differentiated or with less clearly defined phenotypes.• What does this study add? The pathogenic role of chronic hyperuricemia in the development and maintenance of PsA is based on epidemiological, clinical, and fundamental arguments and hence does not appear fortuitous. These two pathological processes can influence each other.• How might this impact on clinical practice? This new line of thinking regarding the convergence of gout and PsA, involving the role of urate crystals, could prompt a potential new approach to treatment (urate-lowering therapy) among patients with active/refractory PsA.

Metabolome Analysis Reveals Dermal Histamine Accumulation in Murine Dermatitis Provoked by Genetic Deletion of P-Glycoprotein and Breast Cancer Resistance Protein

PURPOSE

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are xenobiotic transporters which pump out variety types of compounds, but information on their interaction with endogenous substrates in the skin is limited. The purpose of the present study was to clarify possible association of these transporters in dermal accumulation of inflammatory mediators.

METHODS

Dermatitis model was constructed by repeated topical application of oxazolone in wild-type, and P-gp and BCRP gene triple knockout (Mdr1a/1b/Bcrp^-/-) mice to observe difference in phenotype. Target metabolome analysis of 583 metabolites was performed using skin and plasma.

RESULTS

Dermatitis and scratching behavior in dermatitis model of Mdr1a/1b/Bcrp^-/- mice were more severe than wild-type mice, suggesting protective roles of these transporters. This hypothesis was supported by the metabolome analysis which revealed that concentration of histamine and other dermatitis-associated metabolites like urate and serotonin in the dermatitis skin, but not normal skin, of Mdr1a/1b/Bcrp^-/- mice was higher than that of wild-type mice. Gene expression of P-gp and BCRP was reduced in oxazolone-treated skin and the skin of patients with atopic dermatitis or psoriasis.

CONCLUSIONS

These results suggest possible association of these efflux transporters with dermal inflammatory mediators, and such association could be observed in the dermatitis skin.

Erythrodermic Psoriasis Causing Uric Acid Crystal Nephropathy

Background

Erythrodermic psoriasis is a rare and severe variant of psoriasis. It is characterized by widespread skin erythema, scaling, pustules, or exfoliation of more than 75% of the body's surface area. This condition has life-threatening complications to include hemodynamic, metabolic, immunologic, and thermoregulatory disturbances. One metabolic complication, hyperuricemia, occurs from rapid keratinocyte differentiation and infiltration of inflammatory cells into psoriatic lesions. Although renal injury caused by shunting of blood to the skin has been reported, there are no reports of erythrodermic psoriasis causing crystal-induced nephropathy. We present a case of erythrodermic psoriasis and hyperuricemia complicated by uric acid crystal nephropathy.

Case Presentation

A 57-year-old male with long-standing psoriatic arthritis presented with diffuse scaling of his skin. He was being treated with adalimumab, leflunomide, and topical clobetasol, but had recently stopped taking his medications. Physical exam revealed yellow scaling covering his entire body with underlying erythema and tenderness without mucosal involvement. Labs were notable for a creatinine of 3.3 mg/dL, with no prior history of renal disease, and uric acid of 12.7 mg/dL. He was admitted to the intensive care unit given >80% of body surface area involvement and acute renal failure. Despite aggressive fluid resuscitation, renal function did not improve, and creatinine peaked at 4.61 mg/dL. Urine microscopy showed diffuse polymorphic uric acid crystals, consistent with uric acid crystal-induced nephropathy. He was started on rasburicase, urinary alkalinization, and fluids. His renal function improved dramatically; urine output, uric acid, and electrolytes normalized. He was discharged on topical clobetasol and leflunomide and started on secukinumab with little to no skin involvement.

Conclusion

This case presents the rare complication of crystal-induced nephropathy in a patient with erythrodermic psoriasis. Uric acid crystal nephropathy is well described in diseases with rapid cell turnover such as tumor lysis syndrome. It is thought that rapid keratinocyte differentiation and inflammatory infiltration of psoriatic lesions produced life-threatening electrolyte abnormalities similar to tumor lysis syndrome. Early recognition of this rare complication is critical, and aggressive fluid resuscitation, urine alkalinization, and uric acid lowering agents should be administered immediately.

The effect of subcutaneous methotrexate on markers of metabolic syndrome in psoriatic patients - preliminary report

INTRODUCTION

Methotrexate (MTX) has anti-proliferative and anti-inflammatory effects in psoriasis. Moreover, low doses can reduce the risk of developing cardiovascular diseases. It turns out that psoriasis and atherosclerosis have a similar pathogenetic mechanism: the same pro-inflammatory cytokines, Th1 and Th17, are involved in both diseases.

AIM

To evaluate the effects of metabolic markers, protective cytokines (interleukin 10 (IL-10), transforming growth factor β (TGF-β)) and a marker of endothelial damage (endocan) in patients with plaque psoriasis.

MATERIAL AND METHODS

The study included 24 patients aged 27-69 years (9 female, 15 male) with plaque psoriasis. The metabolic syndrome according to the International Diabetes Federation (IDF) was evaluated. The laboratory tests were performed under fasting conditions: C-reactive protein (CRP), glucose, total cholesterol, triglycerides, high-density lipoprotein (HDL), uric acid, endocan, IL-10, and TGF-β. After 12 weeks of treatment with MTX injections 15 mg/week, every patient was assessed with the same laboratory tests.

RESULTS

After treatment we observed a statistically significant increase of endocan and IL-10, but no significant differences in the titer of TGF-β. C-reactive protein was reduced by approximately 54.7%. No improvement of lipid profile was observed, and even a significant increase in triglycerides was noted. Similarly, no significant difference was seen in the case of glucose and uric acid prior to and after treatment.

CONCLUSIONS

Methotrexate in low doses in short-term treatment decreases CRP (anti-inflammatory effect) and increases endocan and IL-10 (potential protective role). Methotrexate is characterized by good efficacy and tolerability in therapy of patients with psoriasis.

Association of Serum Uric Acid Levels in Psoriasis: A Systematic Review and Meta-Analysis

High levels of serum uric acid (SUAC) are frequently detected in patients with psoriasis. However, the relationship between psoriasis and hyperuricemia remains unknown. Here we conducted a meta-analysis to identify the SUAC levels in subjects with psoriasis and to determine whether there is an associated risk between psoriasis and hyperuricemia.A comprehensive search of the literature from January 1980 to November 2014 across 7 databases (MEDLINE, Embase, Cochrane Central Register, and 4 Chinese databases) was conducted to determine whether there is an associated risk between psoriasis and hyperuricemia.Among the 170 identified reports, 14 observational studies were included in this meta-analysis. We found a significant higher SUAC level (MD 0.68, 95% CI 0.26-1.09; P = 0.002) in patients with psoriasis in Western Europe, but no significant differences were found between the East Asia and India subgroup (MD 1.22, 95% CI -0.13-2.56; P = 0.08) or the Middle East subgroup (MD 0.48, 95% CI -0.49-1.44; P = 0.33). Similar results were obtained from the meta-analysis of SUAC levels in subjects with severe psoriasis.Our meta-analysis showed that the correlation between psoriasis and hyperuricemia was either ethnicity- or region-dependent and that patients with psoriasis in Western Europe were more likely to have hyperuricemia.

P2Y6 receptor signaling pathway mediates inflammatory responses induced by monosodium urate crystals

Gout occurs in individuals with hyperuricemia when monosodium urate (MSU) crystals precipitate in tissues and induce acute inflammation via phagocytic cells such as monocytes. MSU crystals have been demonstrated in skin diseases such as tophaceous gout or psoriasis; however, the importance of MSU crystals in the skin is totally unknown. In this study, we found that MSU crystals, through P2Y(6) receptors, stimulated normal human keratinocytes (NHK) to produce IL-1α, IL-8/CXCL8, and IL-6. P2Y(6) receptor expression increased in MSU-stimulated NHK. Both P2Y(6)-specific antagonist and P2Y(6) antisense oligonucleotides significantly inhibited the production of IL-1α, IL-8/CXCL8, and IL-6 by NHK. Similarly, the P2Y(6)-specific antagonist completely inhibited the MSU-induced production of IL-1β by THP-1 cells, a human monocytic cell line. Remarkably, the P2Y(6)-specific antagonist significantly reduced neutrophil influx in both mouse air pouch and peritonitis models. Thus, these results indicate that the P2Y(6) receptor signaling pathway may be a potential therapeutic target for MSU-associated inflammatory diseases, such as tophaceous gout.

Cross-sectional study on the correlation of serum uric acid with disease severity in Korean patients with psoriasis

BACKGROUND

Hyperuricaemia is a common finding in patients with psoriasis. However, previous studies have reported inconsistent results about the association between serum uric acid concentration (SUAC) and psoriasis severity. Recent studies have also reported that SUAC is associated with metabolic dysregulation.

AIM

To assess any association between SUAC and clinical features of psoriasis, and to investigate the characteristics of patients with psoriasis with hyperuricaemia compared with similar patients with normouricaemia.

METHODS

Cross-sectional data from 198 Korean patients with psoriasis who visited our clinic were analysed. Association of SUAC with clinical features of psoriasis, body mass index (BMI) and various laboratory values was assessed in both genders separately.

RESULTS

The average uric acid concentration of patients with psoriasis was not significantly different from that of the healthy population, for both genders (P > 0.05). There was a positive correlation between SUAC and Psoriasis Area and Severity Index (PASI) and BMI in patients with psoriasis (P < 0.05). There was no association with age of disease onset, family history of psoriasis, or other laboratory values (P > 0.05), in either gender. Of the other factors of disease severity, the extent of body surface involvement was correlated with uric acid concentration (P < 0.05) although there was no significant relationship with activity of individual lesions (P > 0.05). Mean PASI and extent of psoriasis were increased in hyperuricaemic compared with normouricaemic patients (P < 0.05).

CONCLUSIONS

SUAC in patients with psoriasis is positively associated with PASI, extent of skin involvement and BMI for both genders independently.

Comorbidities associated with psoriasis: an experience from the Middle East

Recent studies suggest that psoriasis patients have higher rates of comorbidities. We sought to determine the prevalence of comorbidities and co-medications in our psoriasis patients. We conducted case-control study in 1835 patients with psoriasis vulgaris and age- and gender-matched cohort without psoriasis. Patients were examined for clinical characteristics of psoriasis, PASI scores, and data of age, sex, body mass index (BMI), smoking status, comorbidities, and co-medications were analysed for both patients and controls. We identified 1661 (92.8%) patients with mild to moderate psoriasis (PASI < 10) and 129 patient's (7.03%) with severe psoriasis (PASI > 10). Patients with psoriasis were more likely to be current smokers (51.34% vs 32.51% controls). Respective prevalence rates of risk factors in those with mild-moderate psoriasis, severe psoriasis, and controls were as follows: inflammatory arthritis (20%, 31% and 10.68%); coronary heart disease (4.1%, 8.35% and 1.42%); obesity (BM1) (32.5%, 41% and 17%); diabetes mellitus type II (37.4%, 41% and 16%); hypertension (32%, 40.3% and 11.55%); dyslipidemia (14.1%, 22.48% and 4.96%); metabolic syndrome (16%, 26.35% and 6.76%); chronic obstructive pulmonary disease (COPD) (5.36%, 6.98% and 4.03%); cancer (0.3%, 1.55% and 0.16%). They had a higher odds of inflammatory arthritis, coronary heart disease, obesity, diabetes mellitus II, hypertension, dyslipidemia, and metabolic syndrome. They were receiving significantly wider varieties of drugs. Which most commonly included antidiabetic drugs, antihypertensives, and hypolipidemic drugs.

Increased xanthine oxidase in the skin of preeclamptic women

Xanthine oxioreductase is the holoenzyme responsible for terminal purine catabolism. Under conditions of metabolic stress or heightened proinflammatory cytokine production, this enzyme is preferentially in its oxidized form, xanthine oxidase, with catalytic action that generates uric acid and the free radical superoxide. As preeclampsia is characterized by heightened inflammation, oxidative stress, and hyperuricemia, it has been proposed that xanthine oxidase plays a pivotal role in this hypertensive disorder of pregnancy. We sought to determine whether xanthine oxidase protein content was higher in maternal tissue of preeclamptic mothers, compared to healthy pregnant controls, using immunohistochemical analysis of skin biopsies. We further compared xanthine oxidase immunoreactivity in skin biopsies from preeclamptic women and patients with several inflammatory conditions. In preeclamptic women, intense xanthine oxidase immunoreactivity was present within the epidermis. By contrast, only very faint xanthine oxidase staining was observed in skin biopsies from healthy pregnant controls. Further, a role for inflammation in the increase of xanthine oxidase was suggested by similar findings of heightened xanthine oxidase immunoreactivity in the skin biopsies from nonpregnant individuals diagnosed with conditions of systemic inflammation. The finding of increased xanthine oxidase in maternal tissue, most likely as the result of heightened maternal inflammation, suggests maternal xanthine oxidase as a source of free radical and uric acid generation in preeclampsia.

An unusual patient with hypothyroidism, tophaceous gout, and marked joint destruction

This report describes a 75-year-old Caucasian man with extensive urate deposits and severe gouty arthropathy that confined him to a wheelchair. Since age 50, he suffered multiple acute gout flares and progressive deformities in his hands, feet, knees, and elbows (tophi). Serum creatinine was 1.4 mg/dL and serum urate 9.4 mg/dL. Conditions known to increase uric acid production (psoriasis, chronic bronchitis) and to decrease uric acid excretion (hypothyroidism, metabolic syndrome, and nephroangiosclerosis) may operate in a single patient, illustrating the dramatic clinical course of untreated gout.

Purine metabolism in heterozygous carriers of hypoxanthine-guanine phosphoribosyltransferase deficiency

The urate pool and daily turnover of urate, together with the rate of incorporation of glycine into urate, were measured in three asymptomatic mothers who had sons with various degrees of deficiency of hypoxanthine-guanine phosphoribosyltransferase activity. Two of these mothers had abnormally increased values for the urate pool, urate turnover, and 24-hour urinary excretion of uric acid. These two mothers also had reduced hypoxanthine-guanine phosphoribosyltransferase activity and increased adenine phosphoribosyltransferase activity in erythrocyte lysates. All three mothers showed an abnormal increase in urate production, as judged by the rate of incorporation of glycinie into urate.

Purine metabolism in female heterozygotes for hypoxanthine-guanine phosphoribosyltransferase deficiency

BACKGROUND

Female carriers of the X-linked recessive disorder hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency show somatic cell mosaicism, and this may cause an increased synthesis of purines. We have examined whether urinary oxypurines could be useful for carrier diagnosis.

METHODS

Carrier testing was performed in 35 women belonging to 16 unrelated Spanish families with at least one subject affected by the Lesch-Nyhan syndrome (11 families, 14 patients) or the Kelley-Seegmiller syndrome (five families, six patients) by means of HPRT and adenine phosphoribosyltransferase activities in hair follicles and/or molecular studies. Plasma and 24-h urinary concentrations of hypoxanthine, xanthine and uric acid were measured while subjects were on a purine-restricted diet.

RESULTS

Mean plasma urate concentrations and 24-h urinary hypoxanthine, xanthine and uric acid excretion rates were significantly higher in 22 heterozygotes than in 13 non-carriers (P < 0.02). Daily urinary oxypurine excretion rates were also significantly higher in heterozygotes than in 12 normal women (P = 0.0011). Cumulative 5-day radioactivity excretion after [8-14C]-adenine infusion was markedly increased in 10 carrier women compared with five normal women (P = 0.0369). The sensitivity of 24-h urinary hypoxanthine and xanthine excretion rates was 86% and 77%, respectively, and the specificity 100% for both tests.

CONCLUSION

Female heterozygotes for HPRT deficiency show an enhanced purine nucleotide degradation and purine overproduction. An elevated hypoxanthine and/or xanthine excretion rate differentiated most heterozygotes for HPRT deficiency from non-carrier women and thus could be useful for carrier diagnosis.

Coexisting psoriatic arthritis, gout, and chondrocalcinosis

The authors describe the case of a 63-year-old Caucasian man with a history of psoriatic arthritis who subsequently developed gout and chondrocalcinosis. This is the first report documenting the simultaneous occurrence of psoriatic arthritis, gout, and chondrocalcinosis in a single patient. The relations of these rheumatic diseases are discussed.

Abnormal serum uric acid levels in children

Measurement of the serum uric acid level, most commonly considered in adult patients, is frequently obtained inadvertently for pediatric patients because it is a standard component of many multichannel chemistry profiles offered by clinical laboratories. Most standard references for normal uric acid values do not take into account the impact of the metabolic changes in children at different ages on the uric acid level. A substantial number of childhood conditions may produce perturbations in the serum uric acid level. Knowledge of normal serum uric acid levels and of the conditions affecting those levels in children enables a more focused pursuit of underlying abnormalities.

Clinical and biochemical aspects of uric acid overproduction

Purine nucleotides are synthesized and degraded through a regulated series of reactions which end in the formation of uric acid. Increased uric acid synthesis may be the result of two major pathophysiological disorders: increased de novo purine synthesis and enhanced purine nucleotide degradation, both of which may be the result of an increased or decreased enzyme activity. In addition, some conditions and disorders associated with uric acid overproduction have been recognized as the result of increased ATP degradation or decreased synthesis of ATP. The clinical manifestations of the diseases leading to excess uric acid synthesis are heterogenous, but symptoms related to uric acid overproduction are always secondary to the precipitation of crystals in soft tissues, joints, and the kidney excretory system. In clinical practice, serum urate concentration and urinary uric acid excretion are used to assess uric acid synthesis, taking into account that a purine-rich diet can be a confounding variable. Quantification of uric acid precursors, such as adenosine, inosine, guanosine, hypoxanthine, and xanthine, in biological fluids and intracellular nucleotides has provided further insight into the metabolic disturbances underlying disorders associated with uric acid overproduction. Additional studies are necessary to define precisely the metabolic derangement in idiopathic uric acid overproduction and to assess fully the consequences of increased purine nucleotide degradation, such as free-radical formation, increased adenosine synthesis, and reduced synthesis of signal transducers.

Psoriatic arthritis of the foot and ankle: analysis of joint involvement and diagnostic errors

Forty-two patients with psoriatic arthritis arthritis who were referred to a tertiary medical center from 1983 to 1987 were reviewed. The foot and/or ankle was the most common site of joint or bone involvement, (N = 36, 86%). Twenty-six of these patients demonstrated bilateral involvement. The foot and ankle was the most common site of initial arthritis (N = 23, 55%). Errors in patient diagnosis were noted and analyzed. Eight patients with foot and ankle involvement were diagnosed and treated for either gout or compression of a digital nerve. Major causes for misdiagnosis included failure to identify psoriatic skin lesions and failure to associate foot and ankle symptoms with psoriatic arthritis.

Histochemistry of reactive oxygen-species (ROS)-generating oxidases in cutaneous and mucous epithelia of laboratory rodents with special reference to xanthine oxidase

Cutaneous and mucous epithelia of various organs of laboratory rodents were analysed histochemically for reactive oxygen species (ROS)-generating oxidases using cerium methods. High activities of xanthine oxidase and also superoxide dismutase were present in orthokeratotic stratified squamous epithelia of skin, lips, esophagus and forestomach and parakeratotic keratinizing stratified epithelia of vagina, tongue and penis. Moreover, activity was found in simple epithelium of the uterus and intestine of rats, mice and guinea-pigs. Moderate activities of monoamine oxidase and D-amino acid oxidase were only seen in enterocytes of large and small intestine, whereas alpha-hydroxy acid oxidase could not be detected at all. With the use of specific inhibitors for superoxide anions-producing xanthine oxidase and H2O2-generating superoxide dismutase it was shown that epithelial cells of all studied external and internal surface epithelia contain a highly effective xanthine oxidase-superoxide dismutase system. It is hypothesized that this system might have a general microbicidal function and might play a special role in tumor promotion of the skin.

Uric acid metabolism in children

The renal excretion of uric acid in children differs quantitatively, and perhaps qualitatively, from that in adult humans. The younger the child, the greater the renal clearance of uric acid and the greater the excretion of uric acid expressed as mg per kg body weight. During infancy, the reduced ability to maximally concentrate the urine may protect against precipitation of uric acid crystals within the kidney. Conversely, the extremely high urinary uric concentrations places the very small infant at jeopardy during sudden increases in the filtered load of uric acid. Understanding the pharmacologic and physiologic modulators of renal uric acid clearance will allow the pediatrician to minimize the risk of uric acid nephropathy, and to understand the implications of uric acid in the serum or urine in children with fluid and electrolyte disorders. Certainly evaluation of serum and urinary uric acid concentrations is essential in any child with acute renal failure.

Hyperuricemia and gout

Gout is a clinical syndrome encompassing a group of metabolic diseases that are all characterized by abnormal uric acid metabolism. In its fullest form, gout is defined by: an increase in the serum urate concentration; characteristic, recurrent, acute arthritic attacks, with monosodium urate monohydrate crystals demonstrable in synovial fluid leukocytes; tophi, usually in and around joints of the extremities, composed of monosodium urate monohydrate deposits; renal disease, often accompanied by hypertension with glomerular, tubular, interstitial, and vascular involvement; and uric acid nephrolithiasis. Any combination of these manifestations may occur, although tophi and urate nephropathy rarely antedate gouty arthritis.

Psoriasis and gout: report of 4 cases

Four patients with a simultaneous occurrence of psoriasis and gout are described. These cases were selected out of a group of 108 gouty in-patients. Clinical and laboratory findings in the reported patients are briefly outlined and this association of diseases is described from the viewpoint of differential diagnosis.

Influence of dietary purines on pool size, turnover, and excretion of uric acid during balance conditions. Isotope studies using 15N-uric acid

Pool size, turnover, and excretion of uric acid were investigated in three normal subjects both during purine-free, isoenergetic liquid formula diet and during additional purine administration by use of isotope dilution techniques. The fractional turnover of the uric acid pool was increased during dietary purine administration suggesting an increased total body uric acid clearance as a result of the increase in renal clearance. Fractional turnover increased more in the female subject than in males, while pool size was increased less. It can be calculated from the results obtained that endogenous uric acid synthesis is not inhibited by dietary purines.

Serum uric acid levels in psoriatic arthritis

Serum uric acid levels were determined in patients with psoriatic arthritis on and off medication, with rheumatoid arthritis on no medication likely to alter serum values, and in patients with uncomplicated psoriasis. Values in males were higher than those in females. A larger prevalence of values above the normal range were seen in males with psoriatic arthritis on uncontrolled medication (13-5%) and in males with rheumatoid arthritis (12%) than in the other groups. The means for both these groups were around the midpoints of the normal range. These findings suggest that hyperuricaemia is not a common characteristic of psoriatic arthritis.

Xanthine oxidase and guanase activities in normal and psoriatic epidermis

Xanthine oxidase and guanase activities in normal and psoriatic epidermis were demonstrated and accurately assayed by the new micro-assay methods which rely on the isolation of 14C-labelled end-products, xanthine and uric acid, from the substrates, hypoxanthine and guanine, by electrophoresis on cellulose acetate membrane using 0.1 M borate buffer, pH 9.0. The average specific activities of xanthine oxidase and guanase in normal epidermis were 10.2 and 55.0 pmol/min/mg protein, respectively, and in psoriatic epidermis, 52.1 and 980.6 pmol/min/mg protein, respectively. Increased activities of these enzymes in psoriatic epidermis suggested that urate formation might be enhanced in the psoriatic lesions resulting from an increased turn-over of nucleic acids.

Treatment of psoriasis with oral mycophenolic acid

Mycophenolic acid (MPA), an inhibitor of purine synthesis, was evaluated for its therapeutic and adverse effects in 29 patients with psoriasis. MPA was administered orally for at least 12 weeks, during which time the daily dose was increased from 1600 to 4800 mg depending on occurrence of adverse reactions. Complete clearing occurred in 1 of the patients, almost complete clearing in 14, definite improvement in 13, slight or doubtful improvement in 1. The full effect of MPA required a median time of 8 weeks (range 5-14). After discontinuing MPA, relapses began at a median time of 4 weeks (range 3-8). The severity of psoriasis was scored on a 0 to 108 scale using a newly devised system. The mean severity and range before treatment was 47 (21-88); after 12 weeks, 15 (0-50). Adjustment of dose on the basis of side effects resulted in a median daily dose of 3600 mg (range 2400-4800 mg; 30-96 mg/kg ideal weight). Characteristic dose-limiting side effects were soft or frequent bowel movements, diarrhea, nausea, and anorexia. One instance of reversible, dose-related leukopenia was identified.

Psoriatic arthritis in severe psoriasis

SUMMARY

Of 100 patients admitted to hospital for treatment of psoriasis, 32 had clinical or radiologic evidence of psoriatic arthritis and 17 had both types of evidence. Eight had radiologic evidence of spinal or sarroiliac involvement without symptoms and seven had clinical evidence of peripheral arthritis without radiologic evidence. Patients with psoriatic sacroilitis and spondylitis were most likely to have typical radiograpic changes. It was concluded that psoriatic arthritis is common in patients with severe psoriasis and that is associated with more extensive skin disease than is found in patients without arthritis.

The radiology of gout. Review article

The radiological features of gout are presented on the basis of a consecutive series of 64 in-patients and a review of the literature. Gout is a painful and potentially crippling disorder. Since fewer patients are referred with a classical acute attack due to the advent of more effective drug therapy, the radiologist may be presented with unusual or atypical cases. It is confirmed that there are no specific radiological features of gout. Provided a high index of suspicion be mai-tained, particularly in those groups of patients in whom secondary gout is common, a combination of signs may allow the diagnosis to be correctly inferred, leading to biochemical confirmation.

Oligaemia, renal failure, and jaundice associated with acute pustular psoriasis

An episode of acute pustular psoriasis in a middle-aged man was associated with cholestatic jaundice and followed by acute tubular necrosis. It is suggested that renal failure was due to oligaemia after the loss of albumin into and from the skin. Fluid balance, central venous pressure, and arterial blood pressure should be monitored in patients with acute pustular psoriasis.

Purine and pyrimidine excretion in psoriasis: a comparison with healthy controls during allopurinol therapy

1 Urinary purine excretion has been investigated in two healthy controls and two patients with psoriasis, one a hyperuricaemic, one a normouricaemic. No difference was detected between the patients and controls. Therapy with allopurinol effectively lowered blood and urinary uric acid levels and produced a deficit in total urinary oxypurine excretion in both controls and patients with psoriasis. The concomitant increase in xanthine excretion was greater than the increase in hypoxanthine excretion and xanthine/hypoxanthine ratios (average 0.70 and 1.0 prior to therapy) were increased by allopurinol to an average of 3.0 and 3.8 respectively in the two groups. Allopurinol also reduced the excretion of 8-hydroxy-7-methyl guanine but no effect on the excretion levels of other minor purine bases was noted. 2 Allopurinol was metabolized similarly by both patients and controls, 84% of the administered allopurinol being accounted for as urinary metabolites. 74% of the drug in the urine was excreted as oxipurinol, 26% as unchanged allopurinol plus allopurinol riboside, the remainder being oxipurinol riboside. 3 Pseudouridine excretion in 25 healthy controls was 86.5 ± 17.8 mg/24 hours. Pseudouridine excretion was not excessive in the patients with psoriasis and was not altered by allopurinol therapy. 4 No abnormality or difference in purine or pyrimidine excretion in either patient was detected prior to or during therapy which could be related to the epidermal lesion.

Molecular variation in relation to purine metabolism

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