A 62-year-old woman presented with a 2-year history of asymptomatic spiny bumps on her flanks, arms, and thighs that arose a few months after she stopped using a tanning bed. She denied any history of radiation, chronic illnesses, or new medications and completed all age-appropriate cancer screenings. There was no family history of similar lesions or malignancy. Physical examination revealed numerous nonfollicular tiny spiny papules akin to church spires on the ventral arms, legs, and flanks (Fig. 1A). There was no facial or acral involvement. Complete blood count, chemistry, thyroid studies, vitamin A, and serum and urine protein electrophoresis results were unremarkable. Histopathology results of shave biopsy tissue revealed discrete foci of vertical parakeratosis emanating atop underlying hypergranulosis (Fig. 1B).
First described by Goldstein in 1967, MMDH is a rare cutaneous eruption characterized by nonfolliculocentric filiform papules. Typically, MMDH is distributed on the trunk and extremities and spares facial and palmoplantar regions (Caccetta et al., 2012). The histopathology of MMDH has been described as focal mounds of parakeratosis atop 'a tented epidermis' (Coutinho et al., 2015) with hypergranulosis, as demonstrated in our case. MMDH typically follows either an autosomal dominant congenital pattern of inheritance or, as is the case with our patient, a sporadically acquired, late-onset presentation. Fewer than 30 cases have been reported, with patients ranging from the pediatric to adult population (Caccetta et al., 2012). The differential diagnosis for digitate keratoses includes lichen spinulosis, spiny keratoderma, hyperkeratotic spicules, trichodysplasia spinulosa, and keratosis pilaris. Lichen spinulosis typically presents in adolescents on the head and neck, is folliculocentric, and is often arranged in ovoid clusters. Spiny keratoderma is acrally distributed and has a strong association with malignancy (Caccetta et al., 2012). Hyperkeratotic spicules arise in older adults, have a predilection for the distal sebaceous nose, and are often associated with multiple myeloma (Caccetta et al., 2012).