Primary localized cutaneous amyloidosis: association with atopic dermatitis.

BACKGROUND Primary localized cutaneous amyloidosis (PLCA) is a chronic pruritic dermatological disorder of unknown aetiology. Genetic mutations in cases of familial PLCA have been mapped to the oncostatin-M receptor (OSMR) β, a subunit of interleukin (IL)-31 receptor. IL-31 has been implicated in the pathogenesis of atopic dermatitis (AD). OBJECTIVES To assess if AD is more prevalent in patients with PLCA compared to patients with other conditions attending the same dermatology clinic. Secondarily, to investigate if the prevalence of AD, severity of itch, morphology and locations of PLCA differ between familial and sporadic forms. METHODS Consecutive patients with the clinical diagnosis of PLCA visiting a dermatology clinic were evaluated by a single investigator. Data on demographics, family history, morphological types and locations of PLCA, and itch score were collected and they were screened for concomitant AD based on history and physical examination. The control population consisted of consecutive patients with diagnoses other than PLCA seen in the same clinic. RESULTS A total of 44 patients with and 97 controls were evaluated. The prevalence of AD in patients with PLCA was significantly higher than in controls, at 75% and 39.2% respectively (OR = 4.66, 95% CI = 2.10 to 10.3, p < 0.0005). The prevalence of AD in sporadic cases was significantly higher than familial cases, at 84.4% and 50% respectively (OR = 5.4, 95% CI = 1.23 to 23.7). Mean itch levels, morphological types and locations of PLCA did not differ between familial and sporadic cases. CONCLUSIONS AD was associated with PLCA and the association was stronger with the sporadic compared to the familial cases.