Workup for older adults with pruritis is variable but can include patch testing to evaluate for contact dermatitis. Prior research has reported a broad range of patch test positivity among older adults with pruritic eruptions, from as low as 34% to as high as 90%1. It has been loosely hypothesized that many older adults may be “patch negative” (exhibit no reactions on patch testing) due to a decreased immune response1. This cohort of patch negative older adults remains poorly characterized in the literature.
This descriptive study sought to better characterize shared clinical and histopathologic features of patch negative older adults to improve understanding of contributing etiologies for itch in this group. Out of 124 adults over the age of 60 who were patch tested at UCSF between 2013 and 2019, the final cohort consisted of 23 adults (mean age: 72.3 y) with nonfocal pruritic eruptions and no reaction on patch testing (Table 1).
Table 1 -
Patient demographics.
| Demographic |
N (%) |
| Age (mean) |
72.30 |
| Male |
14 (60.9) |
| Race |
| White or Caucasian |
17 (73.9) |
| Black or African American |
2 (8.7) |
| Asian |
2 (8.7) |
| Other |
1 (4.4) |
| Declined |
1 (4.4) |
On exam, 95.7% of the cohort had erythematous papules and/or plaques (Table 2). Lesions were most frequently distributed on the trunk (47.8%) and extremities (56.5%). Data on eczema history were available for 17 patients, of whom 11 (64.7%) had no prior history of eczema. Histopathology revealed spongiotic dermatitis in 11 (68.8%) of the 16 patients with documented biopsy results. More than half (52.2%) of patients were treated with phototherapy or systemic immunosuppression. Ultimately, 30% of the cohort was diagnosed as having some form of dermatitis (atopic/nummular/allergic with suspected missed allergen/irritant). Most patients (52.2%) were diagnosed with immunologic eruptions of aging (IEA), a diagnosis of exclusion hypothesized to be related to age associated changes of the immune system2. Although these 2 diagnostic groups did share overlapping features, they were differentiated based on atopic diathesis and distribution of lesions. Each of the patients diagnosed with IEA required targeted immunologic treatment for sustained improvement, further supporting an underlying immunologic driver of IEA. While details regarding the extent of response to each treatment are unknown, patients had durable and successful response to Goeckerman, phototherapy, methotrexate, mycophenolate, and dupilumab.
Table 2 -
Characteristics of dermatitis pruritic eruptions in patch negative older adults.
| Characteristic |
Finding in patch negative population |
% of cohort with finding |
| Morphology |
Erythematous papules or plaques |
22/23 (95.7) |
|
Hyperkeratosis |
2/23 (8.7) |
| Distribution |
Head/neck |
9/23 (39.1) |
|
Trunk |
11/23 (47.8) |
|
Extremities |
13/23 (56.5) |
|
Generalized |
6/23 (26.1) |
| Histopathology |
Spongiotic dermatitis |
11/16 (68.8) |
|
Urticarial hypersensitivity reaction |
5/16 (31.3) |
|
Psoriasiform hyperplasia |
2/16 (12.5) |
| Eczema history |
No prior history |
11/17 (64.7) |
|
Prior history |
6/17 (35.3) |
| Comorbidities |
Cancer history (excluding keratinocyte carcinoma) |
7/23 (30.4) |
|
History of HCV or hepatitis |
3/23 (13.0) |
| Prior treatments |
Systemic meds (methotrexate/dupilumab/prednisone) |
6/23 (26.1) |
|
Phototherapy (UV/Goeckerman) |
6/23 (26.1) |
| Ultimate diagnosis |
Dermatitis (including atopic/nummular/allergic with suspected missed allergen/irritant) |
7/23 (30.4) |
|
Immunologic eruption of aging (IEA) |
12/23 (52.2) |
|
Other |
4/23 (17.4) |
This study was limited by the relatively small cohort size. The racial homogeneity of our cohort is consistent with the overrepresentation of white patients seen at UCSF Dermatology, mirroring the general over-representation of Caucasians in patch test clinics in North America3. It should also be noted that the high proportion of patch negative patients in this cohort who required substantial immunotherapy may be reflective of UCSF’s position as a tertiary care referral center which sees more complex patients, and therefore have limited generalizability. Lastly, despite standardization of the grading of patch test reactions, clinical interpretation of these reactions relies on clinician subjectivity.
The findings detailed in this study, while nonspecific, serve as a steppingstone for dermatology to better understand older adults with patch negative pruritic eruptions. Review of this cohort reveals commonalities in morphology and histology, with many patients needing substantial immunologic treatment. Nomenclature before and after diagnosis was variable. It is likely that this population has systemic immunodysregulation in the Th2 pathway from intrinsic immune system aging, which has been postulated to be an underlying etiology of pruritus among older adults, but unfortunately lacks a serum biomarker or specific skin test for elucidation2. IEA therefore represents a subset of patients with chronic pruritus of unknown origin. Chronic pruritus of unknown origin likely combines the nebulous systems of immune, neuropathic, and barrier related itch that are otherwise uncategorized, and those with IEA are individuals who fail to have other identifiable causes of immunologic overactivity leading to itch. While understudied, proposed treatments mirror those of other Th2 diseases, such as atopic dermatitis, with traditional topical and systemic immunomodulation. Diagnosis of IEA therefore guides therapeutic management such that patients are not treated with empiric pruritic treatments like antihistamines or neuropathic agents that may not work in primary Th2 immunologic disease. Further research is needed to identify the mechanisms behind this ubiquitous presentation and optimize therapeutic management for this clinical population where practices are variable and the field lacks research and consensus.
Conflict of interst disclosure
The authors declare that they have no financial conflict of interest with regard to the content of this report.
References
1. Warshaw EM, Raju SI, Fowler JF, et al. Positive patch test reactions in older individuals: retrospective analysis from the North American Contact Dermatitis Group, 1994-2008. J Am Acad Dermatol 2012;66:229–240.
2. Abel MK, Jelousi S, Berger T, et al. Immunological eruptions of ageing: reframing chronic pruritic rashes in older adults. Br J Dermatol 2021;185:638–639.
3. DeKoven JG, Silverberg JI, Warshaw EM, et al. North American Contact Dermatitis Group patch test results: 2017–2018. Dermatitis 2021;32:111–123.
