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Multiple minute digitate hyperkeratoses: A case report

  • Author(s): Miller, Anne
  • Aires, Daniel
  • Fraga, Garth
  • et al.
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Multiple minute digitate hyperkeratoses: A case report
Anne Miller BS1, Daniel Aires MD2, Garth Fraga MD3
Dermatology Online Journal 17 (5): 1

1. University of Kansas School of Medicine, Kansas City, Kansas
2. Division of Dermatology, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas
3. Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas. gfraga@kumc.edu


Abstract

Multiple minute digitate hyperkeratoses (MMDH) is a rare familial or acquired cutaneous eruption of filiform keratoses, typically across the trunk and extremities. Histopathology, distribution, and history can distinguish it from other digitate keratoses. We describe a case of MMDH and discuss it in relation to other disseminated digitate keratoses.



Case report


Figure 1Figure 2
Figure 1. Numerous digitate keratoses of variable length across the upper back

Figure 2. Fine spiky keratoses across the posterior arm and scapular back

A 59-year-old Caucasian woman presented to her dermatologist with a 5-year history of the development of hundreds of pruritic skin-colored to pale yellow, spiny keratotic projections, distributed across her chest, back, and shoulders (Figures 1 and 2). The keratoses were 0.2-0.5 mm wide and 0.5-3.0 mm tall and cylindrical in shape. The adjacent skin was clear. The patient had a history of uterine and cervical carcinoma, but no history of irradiation or malnutrition. No relatives had any similar eruptions.


Figure 3Figure 4
Figure 3. Biopsy reveals a digitate projection of compact orthokeratin atop a slightly tented epidermis (H&E, x20)

Figure 4. Higher magnification reveals an intact granular layer and absence of dyskeratosis or inflammation (H&E, x200)

Punch biopsy revealed a thick column of compact orthokeratin resting atop a slightly acanthotic epidermis with a preserved granular layer. Epidermis showed slight tenting beneath the keratin horn (Figures 3 and 4), without spongiosis, inflammation, or epidermal dyskeratosis. The keratosis arose directly from the epidermis rather than cutaneous adnexa. We made the diagnosis of multiple minute digitate keratoses. The patient was treated with 6 percent salicylic acid (Salex Lotion) and 0.05 percent tretinoin cream. She was referred for malignancy screening and lost to follow-up.


Discussion

Goldstein described the first case of MMDH in 1967 [1]. He suggested the term “multiple minute digitate hyperkeratoses” because the projections were numerous, and finger-like by physical exam and were comprised of a horn of dense orthokeratin. Since then 28 cases have been described in the literature under a variety of terms including MMDH, post-irradiation digitate keratoses, disseminated spiked hyperkeratosis, minute aggregate keratoses, transient post-inflammatory digitate keratoses, and familial disseminated piliform hyperkeratosis [1-21].

MMDH presents with numerous digitate keratoses across the trunk and limbs with sparing of the face, palms, and soles. The keratoses are skin-colored, rod-shaped, non-follicular, 1 to 5 mm in length, 0.3 to 2 mm in diameter [3], and arise from otherwise normal skin. Histopathology reveals an orthokeratin horn atop a tented epidermis with a preserved granular layer. Although parakeratosis has been described, we believe parakeratosis is rare and cornoid lamellae are never present. An autosomal dominant familial variant shows onset in early adulthood and a sporadic form shows onset in late adulthood. Although most late-onset MMDH is unexplained, one case was temporally associated with etretinate therapy for disseminated superficial actinic porokeratosis [18]. Treatment of MMDH may be difficult and some patients decline therapy. Retinoids and keratolytics have shown some efficacy and spontaneous resolution was reported in two patients [6, 17, 19].

Understanding and diagnosing MMDH is complicated by its resemblance to other digitate keratotic conditions such as lichen spinulosus, phrynoderma, spiny keratoderma, arsenical keratoses, postirradiation digitate keratoses, trichodysplasia spinulosa associated with immunosuppression and polyoma infection, hyperkeratotic spicules associated with hematopoietic neoplasia, and even filiform warts. In 2010, Caccetta and co-workers suggested an algorithm that separated MMDH from other digitate keratoses by its generalized distribution and non-follicular origin [3].

On initial clinical examination, MMDH may be mistaken for such common conditions as keratosis pilaris, filiform verrucae vulgaris, or skin tags. Histopathology reveals non-follicular orthokeratotic horns that rule these out. The resulting differential diagnosis includes MMDH and the other rare eruptive digitate keratoses mentioned above. Multiple minute digitate hyperkeratoses is typically generalized; the only other conditions with widespread multiple keratoses are lichen spinulosus and phrynoderma. Multiple minute digitate hyperkeratoses differs from these in that its horns are non-follicular. Furthermore, in MMDH the horns are taller and more rod-like. Of note, lichen spinulosus horns are typically grouped into discrete plaques, which can also help in differentiating it from MMDH. Phrynoderma has a predilection for the dorsal thighs and forearms and is rare in developed countries; phrynoderma can be confirmed by serum deficiency of Vitamin A.

A variety of rare disorders can produce localized digitate keratoses, as opposed to the generalized keratoses of MMDH. Multiple digitate keratoses of the palms and/or soles suggest spiny keratoderma or arsenical keratoses. Spiny keratoderma is histopathologically indistinguishable from MMDH, but exhibits a completely different (palmoplantar) distribution [22]. Arsenical keratoses may be comprised of orthokeratin, but tend to be wider than they are tall.

Multiple facial digitate keratoses suggest trichodysplasia spinulosa or hyperkeratotic spicules associated with plasma cell dyscrasias, Sézary syndrome, and cryoglobulinemia [23]. The paraneoplastic keratoses contain keratin and paraprotein that form distinctive eosinophilic globules. Trichodysplasia spinulosa is a rare polyoma virus-associated mid-facial spicular eruption seen in immunocompromised patients [24]. Along with a different distribution, histopathology also differs from MMDH in both the follicular location of the spines, as well as the presence of enlarged follicular trichohyaline granules.

Although some authors have proposed a relationship between sporadic MMDH and malignancy and / or inflammatory disorders, this contention was based on a broad definition of MMDH that included disorders that are now recognized as distinct from MMDH. These include the paraneoplastic facial hyperkeratotic spicules described above, as well as post-irradiation digitate keratoses, and palmoplantar spiny keratoderma [6]. Adopting the more stringent criteria proposed by Caccetta et al, our review of the literature did not find compelling evidence for associating MMDH with malignancy or systemic disease. That said, malignancy screening such as a general chemistry panel, complete blood count with differential and microscopic examination of the peripheral blood, serum and urine protein electrophoresis, and chest X-ray can still be considered if so desired. It is advised to make sure that patients are up-to-date on their age-appropriate malignancy screening.

In summary, we describe a new case and an overview of multiple minute digitate hyperkeratoses. Understanding this rare disease has been complicated by the confusing nomenclature and lack of consistent criteria. Multiple minute digitate hyperkeratoses is a distinct condition characterized by hundreds of orthokeratotic digitate hyperkeratoses with a propensity for the upper trunk and proximal extremities. It may present in early adulthood with a familial autosomal dominant inheritance pattern or sporadically in late adulthood. Careful attention to distribution, patient history, and histopathology enables accurate diagnosis.

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