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An introduction to skin and skin disease
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
Black pigment (melanin), a polymer synthesized by melanocytes, protects against solar ultraviolet radiation (UVR). Melanocytes, unlike keratinocytes, do not have desmosomes but have long, branching dendritic projections that transport the melanin they synthesize to the surrounding cells. They originate from the embryonic neural crest. Melanocytes account for 5–10% of cells in the basal layer of the epidermis. Melanin is a polymer that is synthesized from the amino acid tyrosine with the help of a copper-containing enzyme, tyrosinase. Other pigments contribute rarely (e.g. bilirubin in jaundice or pigments derived from drugs such as minocycline or chlorpromazine). Exposure to the sun accelerates melanin synthesis, which explains suntanning. Skin color is mainly due to melanin and blood. The number of melanocytes per unit of body surface area is variable, depending on the site of the body but the density of melanocytes is the same in all humans, irrespective of race. The racial differences in complexion are attributed to the distribution and size of melanosomes, which disperse melanin to the keratinocytes. Melanocytes are completely destroyed in vitiligo. In albinism, melanin synthesis is defective. Localized increase in the synthesis of melanin leads to the development of freckles. Melanocytes in benign proliferation are referred to as nevi, and the malignant ones are known as melanomas.
Neurocutaneous Syndromes With Interstitial Lung Disease
Published in Lourdes R. Laraya-Cuasay, Walter T. Hughes, Interstitial Lung Diseases in Children, 2019
Axillary freckling, another form of cafe au lait pigmentation, can serve as a useful diagnostic aid in the early recognition of neurofibromatosis. Twenty percent of patients with the disease will show these spots in the axillary vault. They measure 1 to 4 mm. Since these areas are not exposed to the sun, they can be differentiated from freckles. This finding is not seen in any other condition and therefore it is pathognomonic of von Recklinghausen’s disease.19
Skin
Published in A. Sahib El-Radhi, Paediatric Symptom and Sign Sorter, 2019
Freckles are dark or brown macules, 2–3 mm in diameter, with poorly defined margins that occur in sun-exposed areas: face, upper back, arms and hands. Lentigines, in contrast to freckles, are larger in size than freckles, unrelated to sun exposure and remain permanently. Both are benign.
Synthesis, computational studies, tyrosinase inhibitory kinetics and antimelanogenic activity of hydroxy substituted 2-[(4-acetylphenyl)amino]-2-oxoethyl derivatives
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Muhammad Rafiq, Yasir Nazir, Zaman Ashraf, Hummera Rafique, Samina Afzal, Amara Mumtaz, Mubashir Hassan, Anser Ali, Khurram Afzal, Muhammad Rizwan Yousuf, Muhammad Saleem, Katarzyna Kotwica-Mojzych, Mariusz Mojzych
Melanin is a pigment, primarily responsible for skin colour. It retains antioxidative and photoscreening effect, therefore, provides skin photo-protection, prevents from injury and, absorbs and transforms harmful UV radiations into harmless heat8. Despite its advantages, increased production and accumulation of pigmentations can cause skin problems such as freckles, age spots, post-inflammatory hyperpigmentation, lentigo and melanoma. UV which stimulates melanin synthesis is reported to cause gene mutation, DNA damage, impaired immune system and cancer9. Pigmentation in metastatic melanoma patients results in short overall and disease-free survival10. Melanin content is correlated with higher disease stage and seems to protect malignant melanocytes from chemo-, radio- and photodynamic therapy11,12. Therefore, inhibition of melanogenesis could be a rational approach for controlling metastatic melanoma, abnormal skin pigmentation and related disorders10.
Current developments in pharmacotherapy for actinic keratosis
Published in Expert Opinion on Pharmacotherapy, 2018
Elena Campione, Alessandra Ventura, Laura Diluvio, Mauro Mazzeo, Sara Mazzilli, Virginia Garofalo, Monia Di Prete, Luca Bianchi
BCC accounts for 75% of cases, and is a slow-growing, locally invasive epidermal tumor with a metastatic rate of < 0.1%. Cutaneous SCC accounts for the rest of cases of NMSC and arises from dysplastic epidermal keratinocytes [3]. In contrast to BCC, SCC has a significant recognized rate of metastasis (0.3–3.7%), the majority of which occur from within a subgroup of high-risk SCC [4]. AKs are considered as in situ SCC, because they are essentially indistinguishable in terms of cytology and are similar for molecular biology; therefore, we can consider AKs as a chronic progressive disease. Skin cancer is almost 10 times more common among Caucasians than intensely pigmented ethnic individuals. Other host factors include history of previous NMSC, family history of skin cancer, and immunosuppression. Some phenotypic features are associated with skin cancer risk, including hair and eye color (through correlation with skin phenotype), freckles, and propensity to sunburn. For each types of NMSC, there are low-risk and high-risk occurrences. Specific treatments will be based on the level of risk for recurrence [1].
Giant Perineal Plexiform Neurofibroma in an 8-Year-Old African Male
Published in Fetal and Pediatric Pathology, 2023
Javier Arredondo Montero, Mónica Bronte Anaut, Carlos Bardají Pascual
Regarding the first existing case [1], it was documented in an asymptomatic 5-year-old male in whom a scrotal tumor was observed during routine examination. There was no personal or family medical history. On examination, multiple freckles and a café-au-lait spot on the right lateral buttock were observed. A cystoscopy was performed in which a urethral defect was observed at the level of the posterior wall in the position where the mass was located. A transscrotal surgical approach was performed and a biopsy of the lesion was taken. After confirming the diagnosis of plexiform neurofibroma, it was decided to perform an inverted Y perineal approach with en bloc resection. The urethra, which had a defect, required surgical repair. The patient evolved favorably.