Validation of Diagnosis Criteria of Functional Itch Disorder or Psychogenic Pruritus

Abstract

Sir The demonstration of the role of the brain in the pathogenesis of pruritus confirms that a psychological component could be present in every case of pruritus (1) and that a specific psychogenic pruritus is possible (2). Unfortuna tely, this diagnosis is too often mislabelled as idiopathic pruritus. In order to try to avoid these misdiagnoses, following consensus meetings the French Psycho Dermatology Group (FPDG) has proposed a definition and 10 diagnostic criteria (3). The FPDG proposed to prefer the words “functional itch disorder” (FID) rather than “psychogenic pruritus” and to define FID as “an itch di sorder, where itch is at the centre of the symptomatology, and where psychological factors play an evident role in the triggering intensity, aggravation or persistence of the pruritus”. The 10 diagnostic criteria can be divided into 3 compulsory criteria and 7 optional ones (Table I). For a diagnosis of functional itch disorder, all of the 3 compulsory criteria and at least 3/7 of the optional ones must be met. METHODS With the aim of validating these criteria, the FPDG asked 3 non-French investigators, who are well-known to treat lot of patients with pruritus and who did not participate in FPDG consensus meetings, to use FPDG criteria in cases with a previous diagnosis of psychogenic pruritus. This diagnosis was made by the investigators using their usual diagnostic approach. Questionnaires were completed by investigators, who were selected in Germany, Poland and Sweden. RESULTS AND DISCUSSION Thirty-one patients were included in the study: 23 women and 12 men. The mean age was 64.2 years, range 19–85 years. Seventeen patients were from the Swedish centre, 10 from the German centre and 8 from the Polish centre. All patients presented with chronic pruritus (more than 6 weeks). This pruritus was sine materia, i.e. not associated with primary skin lesion, in all cases and was generalized or localized. There was no identified cause in all cases. A chronological relationship of the occurrence of pruritus with one or several life events that could have psychological repercussions was found in 16 cases (46%), variations in intensity associated with stress in 16 cases (46%), nocturnal variations in 24 cases (69%), predominance during rest or inaction in 20 cases (57%). A psychological disorder was associated in 26 cases (74%). Pruritus was improved by psychotropic drugs in 21 cases (60%) and by psychotherapy in 5 cases (14%). In all cases, 3 compulsory criteria were present. Twenty-seven patients out of 35 presented with 3 optional criteria or more out of 7 (3 criteria: 7; 4 criteria: 13; 5 criteria: 4; 6 criteria: 3). Compulsory criteria appeared well-defined because they were present in all patients. In 8/35 patients (23%), only 1 or 2 optional criteria were found. We propose to classify the diagnosis of FID as doubtful in these cases. In 77%, FPDG criteria allow to confirm this diagno sis. Among optional criteria, nocturnal variations and predominance during rest or inaction appear as very good clinical criteria because they were reported by 69% and 57%, respectively, of patients. An associated psychological disorder was noted by investigators in 73%. Variations according to stress and a chronological relationship of the occurrence of pruritus with one or several life events that could have psychological repercussions were present in only 46%: it could be more difficult spontaneously to spot such a chronology for patients. The effects of treatments do not appear to be discriminant criteria, but they were not used in most cases (especially psychotherapies). They are useful to confirm diagnosis later and to convert a doubtful diag nosis of FID into a definite one. Hence, FPDG criteria and their repartition between compulsory and optional criteria seem to be adequate and discriminant and their use pertinent and helpful. Further studies are needed to validate these criteria