Nail disorders are prevalent dermatologic complaints and present at any age. 50% of the nail disorders were due to infectious causes, 15% were due to metabolic or inflammatory causes, and 5% were due to pigment disturbances and malignancies. The differential diagnosis of nail disorders is still often a field of incertitude. 1 Clinical evaluation is still an issue in such cases. The nail unit is a greatly specialized structure and there are significant histopathological variations within its components. SO, the mycological assessments, and histopathological examinations are pivotal for the diagnosis of different nail disorders. 1 Two factors can hinder a precise diagnosis of nail disorders. The first factor is that several nail disorders may clinically mimic one another, leading to difficulty in diagnosis. From a practical view, one may consider infectious, inflammatory, and neoplastic processes in the differential diagnosis of a single lesion. So, a biopsy is usually resolve the cell layer that is abnormally found in the nail bed or nail matrix, and it is normally found in the nail fold or hyponychium. 2 The nail biopsy is an essential technique to obtain an accurate diagnosis of clinically ambiguous nail diseases that is not diagnosable by history, clinical examination, and mycology testing , 3 but it is disagreeable with the patient and may lead to scarring and disfigurement of the nail. 4

Striae distensae (SD), also known as stretch marks, are common skin lesions causing significant psychological stress and cosmetic disfigurement. They are common to be seen during pregnancy, rapid weight change, puberty, many other pathological conditions including Cushing disease, anorexia nervosa, even excessive use of certain drugs. Clinically, they appear as either red raised linear bands known as striae rubrae (SR) or white depressed atrophic bands known as striae alba (SA). They were first described histopathologically in 1889. Many theories have been established to explain the etiopathogenesis of SD, yet the exact mechanism is still unclear. Also, many treatment modalities have been applied to reach maximum efficacy with the least side effects. This review article aims to optimize the most recent and accepted concepts on etiopathogenesis and pathophysiology of SD which may help in finding the best lines of management with the most satisfactory outcomes.

The constellations of both major and minor criteria of malignancy are important clues for WDT-UMP diagnosis which could be ascertained by CK 19 immunostaining.

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