A Caucasian female, aged 3 years, presented to our clinic
for evaluation of asymptomatic, slowly enlarging pink
and brown scaly plaques on her trunk and extremities,
which had been present since birth. Past medical history was
significant for environmental allergies and recurrent otitis media
necessitating myringotomy tubes. Active medication list included
loratadine and montelukast sodium. There was no family
history of similar skin lesions.
Upon initial evaluation, the patient was found to have several
irregular, 5 mm to 4 cm, atrophic, hyperpigmented thin plaques
with well-defined borders on the right and left upper arms, lower
legs, left chest, and vulva following a blashkoid distribution
(Figures 1 and 2). There was sparing of the palms and soles.
Pathology showed mild papillomatosis and hyperkeratosis associated
with tiers of parakeratosis extending above foci of a
thinned granular layer and epidermal dysmaturation (Figure 3).
Based on the clinical and pathologic findings, a diagnosis of
generalized linear porokeratosis was rendered.
Linear porokeratosis was first described by Mibelli in 1893,
and then later characterized as a distinct subset of porokeratosis
of Mibelli in 1974.1 The pathogenesis of porokeratosis is
not known. One theory is that porokeratoses arise from a rapidly
spreading clone of epidermal cells, which creates a fold
or groove at the point of contact with normal keratinocytes.
This border is histologically manifested by a coronoid lamella.
2 Somatic recombination may provide a mechanism for the
development of epidermal clones.3 Most types of porokeratosis,
including disseminated superficial actinic porokeratosis,
porokeratosis of Mibelli, porokeratosis palmaris et plantaris
disseminata, and punctate porokeratosis have an autosomal
dominant inheritance pattern. Congenital porokeratosis likely
results from genetic mosaicism.4
Numerous modalities have been used to treat porokeratoses
with varying success. These include topical 5-fluorouracil,
topical imiquimod, topical and oral retinoids, photodynamic
therapy, surgical excision and destruction, and carbon dioxide
laser therapy. For our patient, treatment with tretinoin 0.025%
cream was initiated to one area of involvement. She has yet to
follow up in our clinic.