Arsenical Keratosis
Arsenical keratosis is a distinctive acquired, precancerous keratotic skin condition caused by chronic build-up of arsenic in the body. Among potentially malignant skin disorders, it ranks at the top for its ability to progress to multifocal cutaneous squamous cell carcinoma (cSCC), Bowen disease (cSCC in situ) and basal cell carcinoma (BCC).
From an epidemiological and public health standpoint, chronic arsenic poisoning (arsenicosis) from untreated groundwater is a serious health problem in many areas, notably the Red River and Mekong deltas. Arsenical keratoses appear after 10–30 years of exposure and act as a clinical biomarker, warning not only of multifocal skin cancer but also of internal malignancies (lung, bladder, liver).
At Haute-Derma, our comprehensive workup combines trace heavy-metal measurement, multi-site dermoscopic screening and biopsy with immunohistochemistry (p53/Ki-67), followed by superpulsed CO2 laser and/or oral retinoid treatment to bring precancerous skin lesions in arsenic-exposed patients under effective control.
Clinical and Pathological Features
Causes and Mechanisms of Toxicity
- Sources of chronic exposure:
- Household drinking water: Well water that has not been filtered for arsenic, in areas where the ground naturally contains arsenic.
- Traditional or herbal remedies of unknown origin: Some folk remedies contain arsenic trioxide.
- Occupational: Exposure in pesticide manufacturing, wood treatment and metal smelting.
- How arsenic damages cells and causes cancer (carcinogenesis):
- Blocking DNA repair enzymes: Inorganic arsenic binds to the sulfhydryl (-SH) groups of DNA repair enzymes and antioxidant enzymes (glutathione peroxidase).
- Triggering damaging oxidative chain reactions (ROS): This promotes double-strand DNA breaks and mutations in the tumor suppressor gene TP53.
- Epigenetic alterations: Arsenic disturbs DNA methylation (hyper- and hypomethylation), silencing tumor suppressor genes such as p16INK4a.
- Very high affinity for keratin: Arsenic accumulates heavily in cysteine-rich tissues such as skin, hair and nails, driving abnormal keratinocyte proliferation.
Clinical Features
Skin lesions appear late (10–30 years after exposure), alongside other signs of chronic arsenic poisoning:
- Wart-like or horny keratoses on the palms and soles (palmoplantar keratosis):
- This is the most characteristic (pathognomonic) sign.
- Pale-yellow, gray-brown or skin-colored keratotic papules or plaques, 2–10 mm across, with a rough, hard surface, distributed symmetrically on both sides.
- In advanced stages, the papules merge into thick, raised, flower-like or wart-like keratotic plaques (corn-like / punctate keratosis).
- Associated pigment changes (arsenical pigmentation):
- Raindrop pigmentation: Dark brown to black spots scattered over the body (chest, back, abdomen).
- Interspersed with small pale spots, creating a "raindrops on a dusty road" appearance.
- Nail changes: Transverse white bands across the nails (Mees' lines).
- Multifocal malignant transformation:
- The keratotic papules gradually enlarge, crack, bleed or ulcerate → progressing to Bowen disease (cSCC in situ), invasive cSCC or superficial BCC.
- Oncologic profile: Patients with arsenical keratosis often develop multiple skin cancers, including on covered, non-sun-exposed skin.
Histopathology
- Hyperkeratosis and papillary acanthosis: A very thick stratum corneum (with or without retained nuclei) and a thickened epidermis with elongated rete ridges.
- Keratinocyte dysplasia:
- Keratinocytes in the basal and spinous layers lose polarity and show enlarged, hyperchromatic, irregular nuclei with abnormal mitoses.
- Prematurely keratinized (dyskeratotic) cells within the epidermis, with strongly eosinophilic cytoplasm.
- Overlap with actinic keratosis or Bowen disease:
- Mild cases: resemble actinic keratosis.
- Severe cases: resemble Bowen disease (full-thickness epidermal dysplasia without breach of the basement membrane).
Differential Diagnosis and Immunohistochemistry (IHC)
| Condition | Distinguishing Microscopic Features, IHC Markers and Tests |
|---|---|
| Arsenical keratosis | Punctate keratoses on the palms/soles + raindrop pigmentation; arsenic in hair/nails/urine (+); p53 mutant pattern; markedly raised Ki-67. |
| Actinic keratosis (AK) | Only on chronically sun-exposed skin (face, neck, backs of the hands); palms and soles spared; no generalized raindrop pigmentation. |
| Hereditary palmoplantar keratoderma (PPK) | Onset in early childhood; clear family history; no pigment changes or heavy-metal poisoning. |
| Common wart (verruca vulgaris) | Koilocytes in the upper epidermis; rete ridges pointing toward the center; HPV PCR (+) (HPV 2/4). |
| Invasive cutaneous SCC | Atypical cells breaking through the basement membrane into the dermis; p63 (+); p40 (+). |
Our Approach to Treating Arsenical Keratosis
Haute-Derma manages arsenical keratosis on two principles: cutting off the source of exposure and screening systematically for cancer:
- Removing the source of arsenic is essential: Stop using untested groundwater or well water immediately and switch to clean water treated with a dedicated ion-exchange or RO filtration system.
- Regular screening for multifocal skin cancer and internal cancers: Because arsenic causes cancer throughout the body, patients receive total body photography of the skin, along with regular screening for bladder cancer (urine cytology) and lung cancer (chest X-ray/CT).
- Destroying precancerous lesions before they become invasive: Using tissue-sparing techniques such as superpulsed CO2 laser combined with systemic retinoid therapy.
How Arsenical Keratosis Is Diagnosed at Haute-Derma
- Exposure history and clinical examination: We ask about well-water use and where you have lived (high-arsenic areas), and look for the classic triad: palmoplantar keratoses + raindrop pigmentation + Bowen disease/cSCC.
- Measuring arsenic in samples: Arsenic levels in hair and nails (reflecting chronic past exposure) and in a 24-hour urine collection (reflecting recent exposure).
- High-resolution dermoscopy:
- Keratotic papules: grayish-white scale, a nodular surface and tiny dotted vessels.
- Signs of malignant change: surrounding inflammatory redness, irregular hairpin vessels, ulceration or a crater-like central keratin plug.
- Skin biopsy and immunohistochemistry: Thickened papules suspicious for malignant change are biopsied, and p53 and Ki-67 staining is used to grade the degree of epidermal dysplasia.
Specialized Treatments at Haute-Derma
- Systemic retinoids (acitretin / isotretinoin): Acitretin is the core medical treatment. It regulates epithelial differentiation, normalizes palmoplantar hyperkeratosis and helps prevent new cSCC/BCC skin cancers.
- Superpulsed CO2 laser ablation (UltraPulse): Precisely vaporizes hard, thickened keratoses on the palms, soles or trunk. Removing the keratin quickly relieves pain and cracking.
- Photodynamic therapy (PDT): The photosensitizer 5-ALA is applied and then activated with red light. Very effective for widespread arsenical keratoses or patches of Bowen disease on the trunk.
- Mohs surgery / wide excision: For lesions that have already become invasive cSCC or BCC.
- Supportive antioxidants and detoxification: Selenium and vitamin E supplements help reduce arsenic's toxicity to cells by neutralizing ROS free radicals.
