Acne is a disease that can be seen in the first year of age, early childhood, prepubertal age and puberty. Neonatal acne is due mainly to considerable sebum excretion rate, and infantile acne because of high androgens of adrenal origin in girls and of adrenal and testes in boys. These pathogenic mechanisms are characteristic in these ages. Important factors like early onset of comedones and high serum levels of dehydroepiandrosterone sulfate are predictors of severe or long-standing acne in prepubertal age. Hereditary factors play an important role in acne. Neonatal, nodulocystic acne and conglobate acne has proven genetic influences. Postadolescent acne is related with a first-degree relative with the condition in 50% of the cases. Chromosomal abnormalities, HLA phenotypes, polymorphism of human cytochrome P-450 1A1 and MUC1 gene are involved in the pathogenesis of acne. Several other genes are being studied.
A 49-year-old man presented with neurosis, hyperpigmentation of the skin, and depigmentation of the hair. On examination, hyperpigmentation was observed on the oral mucosa and the skin of the forearms, elbows, palmar creases and periunguinal area, knees, and feet. He had megaloblastic anemia with a low serum level of vitamin B12 due to malabsorption resulting from a gastrectomy 10 years previously. His hyperpigmentation was resolved with vitamin B12 supplementation. Histology showed an increase of melanin in the basal layer. In electron microscopic study, many melanosomes were observed in melanocytes and surrounding keratinocytes. We consider that the dominant mechanism of hyperpigmentation due to vitamin B12 deficiency is not a defect in melanin transport but is rather an increase in melanin synthesis.
Of 131 patients with non-segmental vitiligo studied, 29 (22%) had a family history of this disorder. The clinical features and HLA antigens were assessed, and a comparison made between patients with familial and those with non-familial, non-segmental vitiligo. Familial patients developed skin lesions significantly earlier than non-familial patients. There was a significant association between HLA-B46 and familial non-segmental vitiligo, whereas HLA-A31 and CW4 were found in non-familial patients. The differences in clinical features and HLA phenotypes suggest heterogeneity in the pathogenic process between familial and non-familial vitiligo patients.
Polymorphic epithelial mucin (PEM) or MUC1 is a glycoprotein secreted from various epithelial gland tissues. In skin, PEM is detected in sweat glands and sebaceous glands by the DF3 monoclonal antibody. The gene of PEM includes an allele exhibiting length polymorphism due to a variable number of tandem repeats (VNTR); this is expressed co-dominantly, which may influence the microenvironment of the skin. The allelic size variation of the PEM gene was investigated in Japanese acne patients, atopic dermatitis patients, and healthy controls. The frequency of longer length alleles was significantly higher in severe acne patients.
Although human NK cells lyse a wide spectrum of target cells, the precise target structure recognized by NK cells has not yet been elucidated. In order to define a possible relationship between gangliosides on human target cells and susceptibility to NK lysis, 14 human leukemia and lymphoma cell lines were studied. A significant correlation was observed between the quantity of ganglioside GM2 on the target cells and sensitivity to NK lysis. In a single-cell binding assay purified GM2 specifically inhibited human NK cell binding to K562 target cells while other gangliosides did not inhibit binding. The competitive inhibition of NK cells by GM2 was restricted to the source of tissue from which GM2 was isolated. These results indicate that GM2 is a strong candidate as a target recognition structure for human NK cells.
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