Comment on: “Chronic pruritus of unknown origin (CPUO): Uniform nomenclature and diagnosis as a pathway to standardized understanding and treatment”

Plasma metabolomic profiling reveals a novel circulating biomarker signature in chronic pruritus of unknown origin

Chronic pruritus of unknown origin (CPUO) is characterized by chronic itch for 6 weeks or greater without an identifiable primary cause. Studies are needed to investigate circulating blood biomarkers to elucidate disease pathogenesis. The objective of this study was to investigate changes in circulating blood metabolites in CPUO patients and to identify potential therapeutic targets. Our cross-sectional study collected plasma from 11 CPUO patients and 11 matched control patients for mass-spectrometry based metabolite data analysis. 15 metabolites differed significantly in the blood of CPUO patients compared to controls, including nine amino acids (isoleucine, L-tyrosine, threonine, DL-tryptophan, L-valine, methionine, glycine, lysine, and L-phenylalanine), four amino acid derivatives (creatinine, DL-carnitine, acetyl-L-carnitine, and indole-3-acrylic acid), and two aromatic and fatty acid derivatives (2-hydroxycinnamic acid and oleamide). These metabolites were also correlated with itch severity. Metabolic set enrichment analysis (MSEA) identified downregulation of several pathways in CPUO: phenylalanine, tyrosine, tryptophan biosynthesis; catecholamine biosynthesis; and glycine, serine, and threonine metabolism. Our study identified decreases in several circulating plasma metabolites in CPUO patients and downregulation of pathways related to catecholamine biosynthesis and tryptophan biosynthesis, providing insight into the pathogenesis of CPUO.

Chronic eyelid and ocular itch

Chronic eyelid and ocular itch affect many patients seeking dermatologic or ophthalmologic care and have a high burden on patient quality of life. Clinicians should consider the broad range of possible diagnoses when approaching the patient with itch of the eyes or eyelids lasting more than 6 weeks. Allergic conjunctivitis and allergic contact dermatitis are the most common causes of chronic itch of the eyes and eyelids, respectively. Other diagnoses to consider include atopic dermatitis, xerosis, neurogenic itch, dry eye syndrome, seborrheic dermatitis, blepharitis, rosacea, lichen simplex chronicus, and papulosquamous disorders. If no organic cause can be elucidated, diagnoses of psychogenic pruritus or chronic pruritus of unknown origin may be considered. Herein, we discuss the possible etiologies of chronic eyelid and ocular itch inclusive of clinical presentation, diagnostic considerations, and current therapies.

Health-Related QOL and Economic Burden of Chronic Pruritus

Chronic pruritus (CP) has considerable implications for QOL. However, its impact on health-related QOL and economic burden is not fully characterized. We administered a cross-sectional survey on 132 patients with CP using the Health Utilities Index Mark 3 instrument. Normative data from healthy adults (n = 4,187) were obtained from the Joint Canada/US Survey of Health. Quality-adjusted life-year loss and economic costs were estimated on the basis of Health Utilities Index Mark 3 scores of patients with CP versus controls. Patients with CP had lower overall health performance than the control (0.56 ± 0.03 vs. 0.86 ± 0.003, P < 0.001). In multivariable regression, CP was associated with worse overall health performance (coefficient = -0.30, 95% confidence interval = -0.33 to -0.27), most accentuated in the domains of pain (coefficient = -0.24, confidence interval = -0.28 to -0.21) and emotion (coefficient = -0.11, confidence interval = -0.13 to -0.10). The reduced Health Utilities Index Mark 3 score correlated with 5.5 average lifetime quality-adjusted life-years lost per patient. Using conservative estimates for willingness to pay, the quality-adjusted life-year loss translated to an individual lifetime economic burden of $274,921 and a societal burden of $88.8 billion. CP is associated with significant QOL impairment. The economic burden of CP highlights the necessity for further research into management options.