Abstract Background: Little is known about the ultrastructure of pili annulati. Objectives: To examine with transmission electron microscopy affected hairs of a family, whose diagnosis had been confirmed in five individuals with scanning electron microscopy, which showed surface undulations with ‘‘curtain-like’’ folding of the hair cuticula and to compare the findings with normal control. Methods: Hairs of two affected patients and one control were embedded in resin and cut lengthwise to produce ultra-thin sections. Results: The normal hair showed a parallel arrangement of dark lines associated with less electron-dense wide bands. Small cavities could be observed, mostly in the dark lines, affected hairs had a large number of cavities, associated or not with the insertion of melanosomes and loss of parallelism of the dark lines. Higher magnification showed a significant loss of this parallelism, resembling ‘‘wood grooves’’. Widened dark lines were observed in some areas. Study limitations: Only a few hairs were examined. Conclusions: The present results suggest that the microcanaliculi of the hair surface, easily found with scanning electron microscopy, may be secondary not only to the cavities seen in the sections but also to the disorder of proteins that form this region, demonstrated by the changes of the cortex dark lines.

Abstract Panitumumab is a monoclonal antibody against the epidermal growth factor receptor used in metastatic colorectal cancer; in addition to tumor cells, it acts on epidermal keratinocytes and on the outer root sheath and presents skin toxicity in up to 90% of cases. A scanning electron microscope was used to examine the eyelashes and hairs of a 65-year-old patient with eyelash trichomegaly, curly hair, and paronychia undergoing treatment with panitumumab. Grooving in the hair shafts were identified, which were more evident in the eyelashes. Similar to oral epidermal growth factor inhibitors (erlotinib and gefitinib), panitumumab can cause acquired pili canaliculi.

Abstract McCune - Albright syndrome is a genetic disease with cutaneous mosaicism caused by post-zygotic activating mutations in GNAS locus, it has a triad of fibrous bone dysplasia, café-au-lait macules and precocious puberty. We examined a 22-year-old female patient with café au lait spot in right side of the abdomen, with a chessboard - like distribution, extending to right thigh with geographical contours, she has also an ovarian cyst, scoliosis and truncal obesity. Biopsies were taken from the hyperpigmented area and processed for light microscopy and for transmission electron microscopy. Light microscopy showed increased melanin pigment with HE staining. Immunohistochemistry with melanocytic markers (HMB-45 and Melan-A) revealed a normal number of melanocytes. Transmission electron microscopy demonstrated normal epidermal structures, such as desmosomes, cytokeratin filaments and hemidesmosomes. With high magnifications an irregular melanossomal contour was seen, with some indentations in their outline.

Abstract A 73-year-old male patient developed a poorly differentiated squamous cell carcinoma in the anal canal nine months ago. He was treated with two cycles of 5-fluorouracil and cisplatin and concomitant radiotherapy (6 MeV linear photon accelerator, total dose of 54 Gy), with complete remission. Since forty-five days he presentes a painful perianal and intergluteal erosion with circinate pustular borders. Light microscopy showed pseudoepitheliomatous hyperplasia of the epidermis with microabscesses of inflammatory cells (neutrophils and eosinophils) and acantholytic keratinocytes . Indirect immunofluorescence was positive for IgG, with an intercellular pattern, 1:80 titer. The diagnosis of radiotherapy-induced pemphigus vegetans was established and there was significant regression with oral prednisone (40 mg) and topical betamethasone.

Abstract Cutis rhomboidalis nuchae was assessed in a 65-year-old patient. Optical microscopy showed basophilic agglomerations in the reticular dermis with decreased elastic fibers. Trans- mission electron microscopy showed elongated, curved and fragmented structures, and in their interior the presence of electron-dense lumps was reduced and irregular, similar to modified elastic fibers, whereas the collagen fibers had a normal aspect. Scanning electron microscopy showed deposits between the bundles of collagen, resembling pebbles or stones. These findings demonstrate that, at one stage of the disease, the collagen remains normal and the alterations are seen in the elastic tissue.