Contents

SynopsisCodesLook ForDiagnostic PearlsDifferential Diagnosis & PitfallsBest TestsManagement PearlsTherapyReferences

Information for Patients

View all Images (20)

Terra firma-forme dermatosis
Other Resources UpToDate PubMed

Terra firma-forme dermatosis

Contributors: Gil Weintraub MD, Noah Craft MD, PhD, Lowell A. Goldsmith MD, MPH
Other Resources UpToDate PubMed

Synopsis

Terra firma-forme dermatosis (TFFD), sometimes referred to as Duncan's dirty dermatosis, is a condition characterized by asymptomatic, hyperpigmented, dirtlike plaques that are resistant to regular washing with soap and water but easily rub off with 70% isopropyl alcohol.

TFFD is the result of disordered and delayed keratinization of an unknown etiology. TFFD may appear anywhere on the body but is commonly found on the neck, axilla, and trunk. While it occurs more frequently in children and adolescents, it can be found in adults. There are currently no known predisposing risk factors (including age, race, sex, geography, medications, or comorbidities). Although not a life-threatening or contagious condition, it can lead to unnecessary tests (biopsies, endocrine evaluations, etc) and can be cosmetically bothersome for individuals unable to achieve clean-appearing skin.

Codes

ICD10CM:
L85.9 – Epidermal thickening, unspecified

SNOMEDCT:
277905003 – Disorder of keratinization

Look For

Subscription Required

Diagnostic Pearls

Subscription Required

Differential Diagnosis & Pitfalls

  • Dermatosis neglecta – Accumulation of hyperpigmented and adherent scales due to inadequate cleaning or scrubbing of the skin. Often due to underlying physical disability or prior trauma leading to areas going unwashed. Lesions can be removed with vigorous rubbing with soap and water, often repeated over the course of multiple weeks. Dermatosis neglecta may also clear with rubbing of 70% alcohol. When the lesion has persisted in the context of regular washing, TFFD is suggested.
  • Acanthosis nigricans – Brown, velvety plaques arising in the body folds, often serving as a marker of hyperinsulinemia secondary to insulin resistance in obese patients. Treatment of the underlying cause, such as weight, endocrine dysfunction, or underlying malignancy, will reverse skin changes. Acanthosis nigricans does not respond to rubbing with isopropyl alcohol. With acanthosis nigricans, acrochordons (skin tags) are frequently present in involved areas.
  • Pityriasis versicolor – Superficial mycosis from yeast of genus Malassezia, often presenting in warm and humid environments. Pityriasis versicolor can appear as either hyper- or hypopigmented macules. Potassium hydroxide (KOH) prep reveals hyphae and spores, commonly referred to as "spaghetti and meatballs." Pityriasis versicolor responds to topical imidazole or selenium sulfide agents. It does not respond to rubbing with isopropyl alcohol.
  • Seborrheic keratosis – Benign epidermal keratinocyte proliferation that is nearly ubiquitous in older adults. In its early stages, seborrheic keratosis present as small, flat to slightly raised, tan or brown macules that look similar to TFFD. Over time they become increasingly verrucous and elevated, developing a familiar "stuck-on" appearance. While no treatment is necessary, they are easily curetted off. Seborrheic keratosis does not respond to rubbing with isopropyl alcohol.
  • Confluent and reticulated papillomatosis (CARP) – A rare acquired dermatosis characterized by brown papules arranged in a reticulated pattern that localizes primarily in the intermammary, epigastric, and interscapular regions. Most commonly affects young adults, particularly women and people with darker skin phototypes. KOH staining is often negative, but CARP is regularly treated with oral minocycline or erythromycin. CARP does not respond to rubbing with isopropyl alcohol.

Best Tests

Subscription Required

Management Pearls

Subscription Required

Therapy

Subscription Required

References

Subscription Required

Last Updated:12/20/2018
Copyright © 2023 VisualDx®. All rights reserved.
Patient Information for Terra firma-forme dermatosis
Print E-Mail Images (20)
Contributors: Medical staff writer
Premium Feature
VisualDx Patient Handouts
Available in the Elite package
  • Improve treatment compliance
  • Reduce after-hours questions
  • Increase patient engagement and satisfaction
  • Written in clear, easy-to-understand language. No confusing jargon.
  • Available in English and Spanish
  • Print out or email directly to your patient
Copyright © 2023 VisualDx®. All rights reserved.
Terra firma-forme dermatosis
A medical illustration showing key findings of Terra firma-forme dermatosis : Axilla, Brown color, Neck, Scaly plaque, Trunk
Copyright © 2023 VisualDx®. All rights reserved.