Terra firma-forme dermatosis
By Warren R. Heymann, MD, FAAD
Nov. 13, 2024
Vol. 6, No. 46
“Well, Heymann, what do you think?”
When the “acanthosis nigricans” cleared with an alcohol pad swipe, the politest response I could offer was, “He has an excellent prognosis.”
This scenario occurred four years before Duncan et al. named this condition “Terra Firma [dry land]-Forme Dermatosis (TFFD),” detailing the case of a 12-year-old girl with “dirt” on her neck that could not be washed away; this was embarrassing for the patient and her mother. In preparation for a skin biopsy, an alcohol-soaked cotton ball revealed “sparkling clean skin beneath, to the chagrin of any (especially maternal) observers.” (1)
Although TFFD has been referred to as “Duncan’s dirty dermatosis,” despite the dirty appearance, the disorder is not due to the accumulation of “dirt” as seen in “dermatitis neglecta.” TFFD is likely a retention hyperkeratosis resembling acquired ichthyosis. Histologically, TFFD “reveals a disturbed epidermal and corneocyte maturation marked by acanthotic retention hyperkeratosis with lamellar orthohyperkeratosis, corneal keratin globules and whorls. Furthermore, an increased melanin retention with basal hyperpigmentation and melanin pigment deposition into both the papillary dermis (melanophages) and the epidermis up to the dysmaturated corneal layer are commonly observed.” (2)
Dermoscopy demonstrates polygonal plate-like scales in a mosaic pattern. (7) Interestingly, a Wood light examination may demonstrate a whitish fluorescence attributed to “keratin reflectance” (which requires further research). (8) According to Korecka et al., “Ultraviolet-Induced Fluorescence Dermatoscopy is a novel device, which allows observation of skin chromophores. Their output is based on a phenomenon called Stokes shift, which uses the visible light spectrum originating from fluorochromes emitting UV-excited luminescence.” Since keratin emits blue fluorescence in UV light, it enables visualization of TFFD by using Ultraviolet-Induced Fluorescence Dermatoscopy (365 nm), which reveals bright, blue plaques that disappear after wiping the skin with a 70% isopropyl alcohol rub. (9)
The differential diagnoses of TFFD include confluent and reticulated papillomatosis, “dirty neck syndrome” of atopic dermatitis, tinea versicolor, acanthosis nigricans, ichthyosis, seborrheic keratosis, and epidermal nevus. Only TFFD is removed by the application of alcohol. (7)
The etiology of TFFD is unknown, although there may be an association with asthma and allergic rhinitis. (10) Could filaggrin variants be at play? Sechi et al. state, “It is also possible that xerosis plays a role in its development with the frequent applications of emollients to flaky skin that mat down the debris. This may then be compounded by the medical advice of a nonaggressive cleansing, which then may diminish the natural shedding of keratinocytes.” (3) I have witnessed this phenomenon in several patients — the worse TFFD gets, the more gingerly they cleanse.
Treatment of TFFD focuses on rubbing alcohol as first-line therapy. Exfoliating creams containing urea, ammonium lactate, salicylic acid, and tretinoin have been utilized. (3,7) Most importantly, reassurance of TFFD’s benignancy and avoidance of unnecessary ancillary tests are paramount.
Point to Remember: Terra firma-forme dermatosis is diagnosed by a simple alcohol wipe. Recognition of this disorder may ease fears and embarrassment and avoid unnecessary diagnostic tests.
Our expert’s viewpoint
Jaime A. Tschen, MD, FAAD
Speculating on the pathogenesis of terra firma-forme dermatosis, I believe that the lipids in the affected stratum corneum might be temporarily altered, explaining the frequently unrelapsing nature of the disease and its response to the alcohol rub test. Future research into the analysis of lipids in affected areas would be interesting. A comparative lipid analysis of affected and normal skin would likely reveal different ratios of waxes and lipids, likely explaining the “unwashable” nature of the lesional skin and its response to a good solvent, notably alcohol.
Duncan WC, Tschen JA, Knox JM. Terra firma-forme dermatosis. Arch Dermatol. 1987 May;123(5):567-9. PMID: 3579334.
Avci P, Wolter M, Wolf R. When dirt is not dirt! Duncan's dirty dermatosis put under the microscope. J Clin Pathol. 2022 Feb;75(2):143-144. doi: 10.1136/jclinpath-2021-207534. Epub 2021 Apr 19. PMID: 33875458.
Sechi A, Patrizi A, Savoia F, Neri I. Terra firma-forme dermatosis. Clin Dermatol. 2021 Mar-Apr;39(2):202-205. doi: 10.1016/j.clindermatol.2020.10.019. Epub 2020 Oct 17. PMID: 34272010.
Kim D, Lee H, Kim YC. Penile Terra Firma-Forme Dermatosis: A Report of Two Cases. Ann Dermatol. 2023 Nov;35(Suppl 2):S352-S354. doi: 10.5021/ad.21.173. PMID: 38061741; PMCID: PMC10727889.
Anjaneyan G, Nayak P. Terra Firma-Forme Dermatosis Over the Glans Penis. Indian Dermatol Online J. 2023 May 25;14(4):574-575. doi: 10.4103/idoj.idoj_522_22. PMID: 37521220; PMCID: PMC10373811.
Chaima K, Chaabouni R, Bahloul E, Boudaya S, Amouri M, Turki H. An unusual pigmented skin lesion on the nipple-areola area. Clin Case Rep. 2023 Apr 12;11(4):e7115. doi: 10.1002/ccr3.7115. PMID: 37064741; PMCID: PMC10090939.
Zhou Y, Zhang J, Zheng L, Yang F. Penile terra firma-forme dermatosis in children. Pediatr Dermatol. 2023 Sep-Oct;40(5):894-896. doi: 10.1111/pde.15277. Epub 2023 Feb 19. PMID: 36805664.
Demircioğlu D, Sezer E, Durmaz EÖ. White fluorescence of terra firma-forme dermatosis under Wood's light: Another case. Photodiagnosis Photodyn Ther. 2024 Feb;45:103884. doi: 10.1016/j.pdpdt.2023.103884. Epub 2023 Nov 10. PMID: 37952810.
Korecka K, Słomiak-Wąsik A, Dańczak-Pazdrowska A, Żaba R, Polańska A. Terra firma-forme dermatosis displays bright blue plaques in Ultraviolet-Induced Fluorescence Dermatoscopy. Australas J Dermatol. 2024 Jun;65(4):393-395. doi: 10.1111/ajd.14233. Epub 2024 Feb 28. PMID: 38419181.
Akçay G, Topal Y, Aydın O. Prevalences of Allergic Disorders in Children with Terra Firma-Forme Dermatosis. Indian J Dermatol. 2021 Jan-Feb;66(1):49-54. doi: 10.4103/ijd.IJD_324_19. PMID: 33911293; PMCID: PMC8061479.
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