Light and electron microscopy of psoriatic skin before and during retinoid (Ro 10-9359) and retinoid-PUVA treatment

Histopathology of psoriasis treated with zinc pyrithione

Psoriasis is still a relatively poorly understood inflammatory dermatosis that is resistant to many therapies. Because the pathogenesis is poorly understood, rational treatment is elusive. Until recently, the North American public was able to achieve successful resolution with an over-the-counter topical preparation marketed for dandruff and seborrheic dermatitis called SkinCap, which has now been withdrawn from the market. The purpose of this study was to examine the histologic changes induced by this preparation in a well-developed psoriatic plaque. Serial punch biopsies were taken over a 2-week period during which time SkinCap was applied topically twice daily. The biopsies were examined histologically, and features were evaluated semiquantitatively. The classic histologic features of psoriasis resolved completely over 2 weeks, with the reversal beginning with disappearance of neutrophils and the most striking finding being prominent apoptosis at 48 hours. The mechanism of this normalization is unknown. Hypotheses include blockage of cytokine and growth factor effect at some level and induction of apoptosis.

312-nanometer ultraviolet B light (narrow-band UVB) induces apoptosis of T cells within psoriatic lesions

Narrow-band (312 nm) ultraviolet B light (UVB) is a new form of therapy for psoriasis, but its mechanism of action is unknown. In a bilateral comparison clinical study, daily exposure of psoriatic plaques to broad-band UVB (290-320 nm) or 312-nm UVB depleted T cells from the epidermis and dermis of psoriatic lesions. However, 312-nm UVB was significantly more depleting in both tissue compartments. To characterize the mechanism of T cell depletion, assays for T cell apoptosis were performed on T cells derived from UVB-irradiated skin in vivo and on T cells irradiated in vitro with 312-nm UVB. Apoptosis was induced in T cells exposed to 50-100 mJ/cm2 of 312-nm UVB in vitro, as measured by increased binding of fluorescein isothiocyanate (FITC)-Annexin V to CD3(+) cells and by characteristic cell size/granularity changes measured by cytometry. In vivo exposure of psoriatic skin lesions to 312-nm UVB for 1-2 wk also induced apoptosis in T cells as assessed by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) reaction in tissue sections, by binding of FITC-Annexin V to CD3(+) T cells contained in epidermal cell suspensions, and by detection of apoptosis-related size shifts of CD3(+) cells. Induction of T cell apoptosis could be the main mechanism by which 312-nm UVB resolves psoriasis skin lesions.

Clinical, light and electron microscopic features of recessive congenital ichthyosis type I

Based on electron microscopic features, recessive congenital ichthyoses have recently been divided into four subgroups designated ichthyosis congenita (IC) types I, II, III and IV. Type II is characterized by cholesterol clefts in the horny cells, type III by perinuclear elongated membranes in the granular and horny cells, and type IV by masses of lipid membranes in granular and horny cells. Clear electron microscopic criteria for type I are lacking, although the presence of lipid droplets in the horny cells has been suggested as a criterion. In the present study we included ichthyosis patients with (i) recessive inheritance, (ii) erythrodermic fine scaling, (iii) lack of fine structural markers of IC types II-IV. Patients with ichthyotic syndromes were excluded. The case material consisted of 21 patients from 14 families. Eight were collodion babies at birth, but three were normal. Nine had ectropion, the flexures were affected in 12, and the palms and soles were thickened in all but one patient. On electron microscopy lipid vacuoles in the horny cells were common, but were absent in four patients. Changes in other lipid-related structures, including keratinosomes, were common. We conclude that currently type I can be diagnosed only by excluding the other types of ichthyosis. Clinically, IC type I corresponds to classical non-bullous congenital ichthyosiform erythroderma, but there is marked heterogeneity among affected individuals.

Keratoderma hereditaria mutilans. Etretinate treatment and electron microscope studies

Keratoderma hereditaria mutilans is a rare inherited cornification disorder characterized by hyperkeratosis of palms and soles with a characteristic "honey-comb" appearance, keratotic constriction furrows of one or more digits (pseudo-ainhum) and threatening spontaneous amputation. Approximately 30 cases have been reported, but the ultrastructural features have not been well characterized. In this article, we describe the clinical, histologic, and ultrastructural findings in our patient. A biopsy specimen taken before treatment with etretinate showed hyperkeratosis with a well-preserved granular layer and acanthosis. Ultrastructural examination disclosed that the spinous cells and granular cells contained marked swollen mitochondria, many desmosomes, and that corneocytes contained many membrane coating granules (MCG) and lipid like vacuoles. After initiation of treatment, considerable clinical improvement was observed, but without significant histologic modification. The principal post-treatment ultrastructural changes were the reduction of mitochondrial swelling in spinous and granular cells and the reduction in the number of MCG in corneocytes. The intercellular spaces showed increased amounts of fine and coarse granular substances. Stimulation of Langerhans cells was observed. Marginal band formation occurred normally after treatment.

Electron microscopy of composite and intranuclear keratohyalin granules in geographic tongue of psoriasis

Composite and intranuclear keratohyalin granules were observed in an electron-microscopic study of geographic tongue of psoriasis. The significance of intranuclear keratohyalin is not known, but it seems to be related to the disturbed proliferation and differentiation of keratinocytes in psoriasis.

A semiquantitative light and electron microscopic analysis of histopathologic changes in photochemotherapy-induced freckles

Photochemotherapy(PUVA)-induced freckles were found in 25 patients (41%) who had received more than 1,000 J/cm2 of PUVA. The patients had been treated with PUVA for more than 2 years, with more than 150 exposures before PUVA lentigines appeared on the thighs, the upper arm, the mid-lower arm, the waist, and the buttocks. The histopathology of these freckles was analyzed by light and electron microscopy. Light microscopy showed an increased amount of pigment and melanophages and increased numbers and size of melanocytes. The keratinocytes often displayed atypical features such as enlarged nuclei, giant size, or fibrillar degeneration. Homogenization of the papillary dermis was observed in 11 patients. The activation of melanocytes was confirmed electron microscopically, and pathological features such as large amounts of lipid droplets and lysosome-melanosome complexes within the melanocytes were seen. The Langerhans cells were mostly normal, whereas the keratinocytes showed cytolytic changes, fibrillar degeneration, and vacuolization. A close follow-up of patients with prolonged PUVA treatment is recommended.

Ultrastructure of pityriasis rubra pilaris with observations during retinoid (etretinate) treatment

The light and electron microscopic structure of pityriasis rubra pilaris (PRP) is described in five patients. Hyperkeratosis, hypergranulosis, keratotic plugs in the follicular openings, acanthosis and focal parakeratosis were observed. A moderate perivascular infiltrate was seen in the upper dermis. Electron microscopy revealed moderately activated keratinocytes, a decreased number of tonofilaments and desmosomes, enlarged intercellular spaces, parakeratosis with lipid-like vacuoles and a large number of keratinosomes. Lymphoid cells were present in the epidermis in moderate numbers. At the dermo-epidermal junction, the basal lamina was focally split, containing gaps. Etretinate therapy produced moderate to marked clinical improvement. The histological picture improved but the typical signs of PRP, including follicular plugging, persisted. Ultrastructurally the cellular activity and the amount of hyperkeratosis and parakeratosis decreased, while increases in keratinosomes, intercellular substance, microvilli and desmosomes were observed during treatment.