This blog series highlights conditions that have a strong impact on people of color and appears as part of Project IMPACT: Improving Medicine’s Power to Address Care and Treatment.
Palmoplantar keratoderma (PPK) is a diverse group of hereditary and acquired disorders characterized by hyperkeratosis of the palmar and plantar skin. While the vast majority are acquired secondary to trauma, infection, neoplastic disorders, or inflammatory dermatoses, a minority are hereditary. Clinically, PPK is classified into diffuse, focal, and punctate palmoplantar keratoderma (PPPK). These entities are further distinguished from one another based on the cutaneous presentation, extracutaneous associations, and presence of epidermolytic keratosis on histopathology. PPPK can affect any skin type, but one subtype of PPPK in particular – PPPK of palmar creases – disproportionately affects Black individuals.
PPPK, or keratosis punctata, is a heterogenous group of benign conditions inherited in an autosomal dominant disorder fashion, with some sporadic cases reported. The diagnosis is made clinically; PPPK is characterized by numerous pinpoint, firm papules over the entirety of the palmoplantar surface. Numerous subtypes have been identified (ie, PPPK type 1, PPPK type 2, PPPK type 3, PPPK of palmar creases).
PPPK type 1: Also known as Buschke-Fischer-Brauer disease, keratosis punctata palmaris et plantaris, and keratosis papulose, patients with this subtype present with discrete, hyperkeratotic papules starting in late childhood and adolescence, although disease onset has been reported in up to the fifth decade of life. Clinically, multiple tiny punctate papules appear, ranging from translucent in appearance to opaque and verrucous over time. Papules can coalesce into a more diffuse pattern over pressure points, in particular on the soles, and variable nail changes may be seen. Often, a central hyperkeratotic core may be visualized. However, as the lesions are aggravated by physical labor or trauma, the core may be lost, leaving behind a central depression or pit. Original papules may continue to enlarge to form callus-like lesions.
PPPK type 2: Also known as spiny keratoderma, music box spine keratosis, and palmoplantar filiform hyperkeratosis, this rare subtype is clinically characterized by pinpoint keratotic projections on the palmoplantar surface. Unlike PPPK type 1, this subtype typically manifests in the fifth decade of life, may be sporadic or inherited in an autosomal dominant fashion, and is associated with various underlying malignancies necessitating regular cancer screenings.
PPPK type 3: Also known as acrokeratoelastoidosis (AKE), PPPK type 3 is a rare genodermatosis that is inherited in an autosomal dominant pattern and characterized by abnormal and decreased elastic fibers in the dermis with elastorrhexis (fragmentation and degeneration of elastic fibers) seen on histopathology. Literature regarding PPPK type 3 is limited, but of the few case reports available, there is no associated age of onset, sex, or racial predilection. Patients clinically present with smooth, skin-colored to yellow, hyperkeratotic papules that coalesce into plaques on the palms and soles, in particular the thenar and hypothenar eminence.
PPPK of the palmar creases: Also known as keratosis punctata of the palmar creases (KPPC), PPPK of the palmar creases is a rare dermatosis of unknown etiology that, unlike the other subtypes, disproportionately affects Black individuals. Clinically, it is characterized by punctate papules localized exclusively to the flexion creases of the palms and digits. These discrete papules have 2-5 mm hyperkeratotic horns that break off, leaving behind small pits or depressions. Biopsy reveals a hyperkeratotic plug depressing the epidermis. Reported associations include Dupuytren contracture and knuckle pads.
Differences in Clinical Presentation in Skin of Color:
Hyperkeratotic papules may appear yellow to light brown in darker skin colors and yellow in lighter skin colors.
What to look for:
PPPK type 1: Tiny punctate papules, ranging from translucent in appearance to opaque and verrucous, with hyperkeratotic cores. Papules may coalesce into a more diffuse pattern over pressure points, in particular on the soles, and variable nail changes may be seen. Often, the core is lost from the papule, leaving behind a central depression or pit. As time progresses, papules may continue to multiply and enlarge to form callus-like lesions. Variable nail changes have been reported.
PPPK type 2: Pinpoint keratotic spines on the palms and soles.
PPPK type 3: Flat to umbilicated, hyperkeratotic, shiny papules ranging in color from yellow to brown. Usually located on the borders of the palms, soles, and toes. Associated nail dystrophy has been observed.
PPPK of palmar creases: Keratotic papules with depressions or pits localized to the creases of the palms and palmar aspect of the fingers.
- Porokeratosis palmaris et plantaris
- Verrucae vulgaris
- Arsenical keratosis
- Callosities and corns
- Palmar pits – Darier disease, basal cell nevus syndrome, pitted keratolysis
- Secondary syphilis
- Keratoderma blennorrhagica
- Aquagenic palmar keratoderma (hereditary translucent acrokeratoderma)
- Acrokeratosis paraneoplastica
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Bodemer C, Steijlen P, Mazereeuw-Hautier J, O’Toole EA. Treatment of hereditary palmoplantar keratoderma: a review by analysis of the literature. Br J Dermatol. 2021 Mar;184(3):393-400. PubMed ID: 32307694
Gao, Yang, S., Li, M., Yan, K. ., Jiang, Y. ., Cui, Y., Xiao, F. ., Shen, Y. ., Chen, J. ., Liu, J. ., Xu, S. ., Huang, W., & Zhang, X. . (2005). Refined localization of a punctate palmoplantar keratoderma gene to a 5·06-cM region at 15q22.2-15q22.31. British Journal of Dermatology (1951), 152(5), 874–878. https://doi.org/10.1111/j.1365-2133.2005.06488.x
Chee SN, Ge L, Agar N, Lowe P. Spiny keratoderma: case series and review. Int J Dermatol. 2017 Sep;56(9):915-919. PubMed ID: 28681429
Nagler A, Boyd KP, Patel RR, Lee HS. Spiny keratoderma. Dermatol Online J. 2013 Dec 16;19(12):20706. PubMed ID: 24364997
Meziane M, Senouci K, Ouidane Y, Chraïbi R, Marcil T, Mansouri F, Hassam B. Acrokeratoelastoidosis. Dermatol Online J. 2008;14(9):11. PubMed ID: 19061593
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Kladney, & Johnson, S. (2018). Keratosis Punctata of the Palmar Creases. Journal of General Internal Medicine?: JGIM, 33(9), 1582–1582. https://doi.org/10.1007/s11606-017-4294-5
This Project IMPACT blog series was created to highlight dermatologic conditions that disproportionately affect people of color. By improving diagnosis in skin of color we can reduce racial disparities in healthcare.
More in this series:
- The Impact of Longitudinal Melanonychia
- The Impact of Nevus of Ito
- The Impact of Nevus of Ota
- The Impact of Lichen Scleroderma
- The Impact of Lichen Planopilaris
- The Impact of Traction Alopecia
- The Impact of Pomade Acne
- The Impact of Acne Keloidalis Nuchae
- The Impact of Pseudofolliculitis Barbae