Punctate porokeratotic keratoderma
- Author(s): Alikhan, Ali;
- Burns, Tracy;
- Zargari, Omid
- et al.
Published Web Locationhttps://doi.org/10.5070/D34nj1z8mr
Punctate porokeratotic keratoderma1. MacNeal Hospital, Berwyn, Illinois. firstname.lastname@example.org
Ali Alikhan MD1, Tracy Burns BS2, Omid Zargari MD3
Dermatology Online Journal 16 (1): 13
2. University of California at Davis, School of Medicine, Sacramento, California. email@example.com
3. PARS Clinic, Rasht, Iran. firstname.lastname@example.org
We report a 29-year-old woman with multiple small keratotic papules on her lateral fingers and first and second toes. Histopathology revealed a compact parakeratotic column with a poorly developed stratum granulosum, indicating punctate porokeratotic keratoderma (PPK). We discuss demographics, etiology, histopathology, differential diagnosis, and treatment of this disease.
|Figure 1||Figure 2|
A 29-year-old woman presented with multiple, firm, 0.5 mm, keratotic papules on her lateral fingers, as well as her first and second toes (Figure 1). The papules, which started on her fingers, have been generally asymptomatic, but occasionally pruritic. She has been dealing with the problem for several years and the recalcitrant nature of the lesions prompted her visit to a dermatologist. She had no family history of these lesions and her past medical history has been uneventful. She has no history of immunosupression, photosensitivity, unexplained weight loss, or signs of any serious medical conditions including malignancies, hyperlidedemia, or hypertension. Failed treatments have included, salicylic acid 5-10 percent in various vehicles, topical steroids, intramuscular triamcinolone, and 5 percent fluorouracil cream. The diagnosis of punctate porokeratotic keratoderma (PPK) was made based on the clinical presentation of the papules and histologic features of the biopsy (Figure 2). Additionally, she is up to date for age appropriate screenings for malignancies, given the risk of paraneoplasia in PPK.
Punctate porokeratotic keratoderma (PPK) is manifested by multiple, small (0.2 - 1.0 cm), firm, flesh-colored, punctate, sharply marginated, keratotic papules of the palms, volar and lateral fingers, and soles [1, 2, 3]. Papules are firmly attached at their bases . Although lesions are not typically symptomatic, they may still distress patients who have gone as far as shaving them [5, 6]. First described in 1971, both sporadic and hereditary cases of PPK have been reported. Males may be affected more often than females [2, 6]; manual labor may also be a risk factor . There is no racial predilection and the age of onset ranges from 12 to 74 [1, 8].
Etiology of the disease is uncertain, but it involves disordered keratinization. Keratins 6 and 16, typically present only in proliferating cells and normal foot sole epidermis, were present in palmar PPK lesions in one study, indicating a hyperproliferative process . In some cases, an autosomal dominant form of inheritance may occur [3, 6, 10]. Sporadic (idiopathic) cases may be a result of UV irradiation, immunosuppression, or neoplastic growth factors . A concerning association exists between PPK, particularly the idiopathic form, and various malignancies, including chronic lymphoid leukemia , bronchial carcinoma [11, 12], squamous cell carcinoma , and ovarian carcinoma , among others . It has also been associated with autosomal dominant polycystic kidney disease  and type IV hyperlipoproteinemia .
Histopathology demonstrates a compact column of hyperparakeratotic cells originating from the stratum corneum and superior epidermis. Beneath the column is an absent or poorly developed granular layer . An abrupt transition to the normal orthokeratotic stratum corneum occurs at the borders of this parakeratotic column [9, 15]. The parakeratotic column typically extends above the adjacent orthokeratotic stratum corneum [6, 10, 11, 12], although in our case it appears almost level. Under polarized light, different birefringence may be noticed between the normal stratum corneum and the parakeratotic columns . Differentiating between PPK and porokeratosis is essential because the latter is associated with basal and squamous cell carcinomas [2, 10]. Although the parakeratotic columns of PPK resemble the cornoid lamellae of porokeratosis, PPK does not have associated dyskeratosis, vacuolated keratinocytes, or underlying lymphocytic inflammation of the papillary dermis [2, 15]. From a clinical standpoint, unlike the lesions of PPK, those of porokeratosis have characteristic, centrifugally expanding rings (annular lesion with raised peripheral hyperkeratotic border), which coalesce to form plaques . Also, PPK is limited to the palms and soles, whereas porokeratosis involves the trunk and limbs. Porokeratosis also tends to develop at an earlier age (early childhood); PPK may develop later on in life.
Unfortunately, lesions do not resolve spontaneously. Treatment is usually unsuccessful, but topical 5-fluorouracil , tacalcitol 0.002 percent ointment , and tazarotene 0.1 percent gel , have been used effectively. Salicylic acid 40 percent ointment overnight followed by curettage in the morning  and salicylic acid 6 percent gel applied under occlusion  have also produced favorable results. If lesions are few and bothersome, complete excision via punch biopsy may be appropriate .
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