OBJECTIVES: Prurigo Nodularis (PN), or chronic nodular prurigo, is a rare chronic skin disease, characterised by multiple itchy, firm nodules, usually with a symmetrically distribution on the torso and the extensor sides of the extremities. PN severely affects the quality of life. The prevalence across countries has been estimated between 8,4-210 per 100.000. We aimed to estimate the prevalence of PN and explore the occurrence as well as the chronology of associated comorbidities at the hospital setting in Denmark.

METHODS: Patients with PN were identified using the ICD10-code L28.1 (PN) as their primary or secondary diagnosis in the Danish National Patient Register (DNPR) between 1995 and 2021. The comorbidities such as diabetes, asthma and chronic obstructive pulmonary disease (COPD), identified before and/or after the first diagnosis with PN, were identified in the DNPR.

RESULTS: During the study period, 1,207 Danish citizens with PN diagnosis were identified (mean age at diagnosis: 59 years, 58% were female). Ultimo 2021, the number was 830 patients (total Danish population 5,900,000) giving a prevalence of 14 per 100.000. A total of 437 (35%) had no associated comorbidities before being diagnosed with PN. After diagnosis, 358 (28%) patients did not have any diagnosed comorbidities. We found that 640 (53%) PN patients were diagnosed with minimum one comorbidity before being diagnosed with PN, while 67% of the PN patients were diagnosed with minimum one comorbidity after diagnosis. Thus, PN is associated with many comorbidities and the three most prevalent were found to be COPD, asthma and type 2 diabetes.

CONCLUSIONS: Using the ICD10-code L28.1 the prevalence of PN is somewhat lower than expected. One explanation could be that a great fraction of patients with PN are categorised with other primary diagnosis such as AD. Two thirds of the identified PN patients had other diseases.