1. Introduction
Pruritus is an unpleasant sensation leading to the need to scratch or rub [1] . According to some authors [2] [3] , pruritus is the most common symptom in dermatology. In fact, a study carried out in Oslo in Norway, showed that pruritus was the most commonly reported symptom (7%) and was much more prevalent in men from East Asia (18%) and slightly less so in North Africa (13%) [4] . In another study, also carried out in Oslo on 18,770 participants, 8.4% of adults aged between 30 and 76 years old surveyed in the general population suffered from pruritus [5] . In contrast, a German study published in 2017 showed that around 13.5% of the general population suffered from chronic pruritus, with an incidence of 7% [6] . Depending on its course, pruritus is either acute or chronic [7] . There are two clinical forms: localised or generalised. Pruritus is said to be generalised sine materia when it affects the whole body and is not accompanied by specific dermatological lesions. It impairs patients’ quality of life. Also known as “naked” pruritus, generalised pruritus sine materia can have many etiologies: systemic (hepatic, renal, haematological, endocrine, iatrogenic), psychogenic, neuropathic or idiopathic [8] . It may be due to an accumulation of toxins (cholestatic or uraemic pruritus) or to exogenous agents (chemicals, drugs). It may therefore be indicative of serious internal illnesses. In Benin and particularly in Parakou, there is little data on the causes of generalised pruritus sine materia. The aim of this study was to identify the etiologies of generalized pruritus sine materia and to determine the factors associated with its occurrence in Parakou Hospital.
2. Materials and Methods
This was a retrospective, descriptive, analytical observational study. Data were collected from January 2011 to June 2022. Patients of any age and sex were included if pruritus was considered to be sine materia after clinical examination, and if an etiological work-up was available or not, either complete or partial. Sampling was carried out by exhaustive recruitment of all the files of patients meeting the inclusion criteria who had consulted a doctor during the study period. The dependent variable was generalized pruritus sine materia and the independent variables were sociodemographic, history, lifestyle, cosmetic habits, clinical aspects and etiologies. For each patient, sociodemographic, clinical and etiological data were collected using a pre-established survey form (Annex 1). The data collected were recorded, processed and analysed using Epi Data 3.1 and SPSS version 21 software respectively. Microsoft Word 2016 and Excel 2016 were used to enter the text and organise the data in the form of tables and graphs. Qualitative variables were analysed independently and presented in the form of numbers (n) and proportions in the population (%) with their 95% confidence intervals. Quantitative variables were presented as means and standard deviations. The Chi-2 test was used to compare proportions. Univariate analysis was used to search for an association between the different independent variables and pruritus sine materia. Values of P < 5% were considered statistically significant. A risk analysis based on the OR parameter and its confidence interval revealed risk factors associated with pruritus sine materia.
3. Results
The hospital incidence of generalised pruritus sine materia was 0.89%, either 73 cases out of 8214 consultants over the 12 years period. There were 38 women and 35 men, either a predominance of women with a sex ratio of 0.92. The average age of patients was 33 ± 14.7 years, with extremes ranging from 3 to 80 years; young adults aged 20 to 35 years (60.3%) were the most represented, followed by those aged 35 to 50 years (18.7%) and those aged 50 to 65 years (7.3%). Patients aged over 80 were the least represented (0.5%). Most of the patients were married, 39 patients (53.4%), and pupils or students predominated (32.9%), followed by the self-employed (21.9%) in terms of socio-professional status. With regard to lifestyle (Table 1), 35.6% of patients drank alcohol and 68.5% of patients washed their bodies twice a day. The majority of patients (54.8%) changed their clothes every 2 days.
Patients were systematically asked to undergo a biological assessment. These included complete blood count, hepatic transaminases, HBsAg, HCV antibody, blood sugar, creatinine, HIV serology, sedimentation rate and parasitological examination of stools. More than half of the patients did not afford the requested tests, which made it difficult to determine the cause. The predominant etiologies (Table 2) were aquagenic pruritus (41.4%), followed by intestinal parasitosis (31.0%) and idiopathic generalised pruritus sine materia (10.4%). Depressive anxious state, viral hepatitis C and martial deficiency were found in 3.4% of patients.
With regard to associated factors, no statistically significant link was found between sociodemographic, socio-cultural or socio-economic data and generalised pruritus sine materia. However, in the lifestyle section, two risk factors were found after bivariate analysis (Table 3 and Table 4): the frequency of changing towels greater than 1 month (OR = 3.02; CI95% = 0.98 - 9.31; P = 0.0486) and the use of cold water for body cleansing (OR = 3.28; CI95% = 1.09 - 9.81; P = 0.0274).
4. Discussion
The prevalence of generalised pruritus sine materia varies widely in the literature. It was low (0.89%) in Parakou, Cotonou (Benin) and Iran [9] [10] , whereas it was higher in Nigeria, Ghana and Togo [3] [11] [12] . This high prevalence in these countries may be linked to the study period, when certain endemic parasitoses, such as onchocerciasis and filariasis, were still prevalent in these regions. According to the literature, the frequent causes of generalised pruritus sine materia are internal diseases, found in proportions of 10% to 50% [10] [11] [12] [13] . These are most often haemopathies, chronic renal failure, hypothyroidism
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Table 1. Distribution of patients suffering from generalised pruritus sine materia according to lifestyle in the Dermatology-Venerology Department of CHUD-B/A from January 2011 to June 2022.
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Table 2. Distribution of patients suffering from generalised pruritus sine materia according to etiology in the Dermatology-Venerology Department of CHUD-B/A from January 2011 to June 2022, N = 29.
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Table 3. Factors associated with generalized pruritus sine materia in the Dermatology-Venerology Department of CHUD-B/A from January 2011 to June 2022.
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Table 4. Factors associated with generalized pruritus sine materia in the Dermatology-Venerology Department of CHUD-B/A from January 2011 to June 2022 (Following).
and martial deficiency. In Parakou, the most frequent etiology was aquagenic pruritus, accounting for 41.4%. This result is comparable to those found by Dégboé et al. in Cotonou (Benin) [9] and Olumide et al. in Nigeria [11] , where aquagenic pruritus was the most frequent etiology (32.5% and 21% respectively). This could be explained by the fact that these different studies were carried out in the same West African context, where the lack of financial resources and the illiteracy of patients constitute a real obstacle to etiological research into generalised pruritus sine materia. In the study population, internal diseases came in second position and were dominated by intestinal parasitosis (31.0%). A prospective study conducted over 12 months by Pitché et al. in Togo [3] had found intestinal parasitosis as the main aetiology in a proportion of 24.75%. In Africa, the importance of parasitosis in the occurrence of generalised pruritus sine materia could be explained by environmental factors (major tropical parasitic endemics, hot, humid climate). Poverty and a lack of individual and collective hygiene are also factors that encourage parasite infestation [14] [15] . According to the literature, pruritus is a cardinal sign of atopy and is known to be a risk factor for pruritus [15] [16] . Olumide et al. in Nigeria made the same observation and noted that the notion of personal atopy was a risk factor for generalised pruritus sine materia [11] . This is in contrast to the results of the Parakou study, where the risk factors were the frequency of changing towels for more than 1 month (P = 0.0486; OR = 3.02) and the use of cold water for bath (P = 0.0274; OR = 3.28). In addition, several authors have noted the rarity of generalised pruritus sine materia in patients under 16 years of age and consider that an age greater than 16 years could be a risk factor for the occurrence of generalised pruritus sine materia [3] [9] [10] [17] [18] . The same observation was made in Parakou, where only 2.3% of patients under the age of 15 had the condition. The limitations of the present study were that the search for generalised pruritus sine material solely in the Dermatology Department of the CHUD-B/A did not allow us to reflect its true prevalence in hospitals, or its various etiologies; similarly, the fact that most patients did not undergo paraclinical examinations was a real obstacle to etiological research.
5. Conclusion
The frequency of pruritus sine materia is not negligible in Parakou. The causes of generalised pruritus sine materia are diverse, with aquagenic pruritus at the top of the list, followed by internal parasitosis. Identifying these when treating patients will undoubtedly improve their quality of life.
Annex 1. Survey Sheet
Generalized Pruritus Sine Materia: Epidemiological, Clinical, Étiological Aspects and Associated Factors in the Dermatology-Venerology Department of Chud-Borgou/Alibori (Benin)