Disorders of Skin Pigmentation MCQs

Ans. D. Becker nevus Becker nevus is appendageal nevi where as other three are melanocyitc nevi. Melanocytic nevi are :- Dysplastic nevus BIue nevus Nevus of ito & nevus of ota Spitz nevus Giant pigmented nevus Mongolian spot Intramucosal neyus

Answer- C. Lipodermatosclerosis The most commonly recognized form of lipodermatosclerosis (LDS), chronic LDS presence with induration and hyperpigmentation of the skin involving the one or both of the lower legs in a characteristic "inverted champagne bottle" appearance. Associated with venous insufficiency, LDS is most common in middle-aged women.

Melanocytes are very susceptible to thermal injury and may die at temperatures below -5 C. As compared to other cells in the skin, including epidermal keratinocytes, merkel cells, langerhans cells, mesissners corpuscles, contact cooling of the skin surface causes selective loss of epidermal melanocytes when the tissue temperature reaches −5 °C or cooler with an exposure time of 10 minutes or longer, leading to partial skin depigmentation Longer exposures combined with colder temperature exposure led to more complete depigmentation in the treated skin surface. This is a reason why cryosurgery procedures on skin - using liquid nitrogen at -196 degrees Celsius - causes depigmentation as a common side effect Reference: Rooks textbook of dermatology 9th edition, chapter 2, page 17

Lichenification is characterized by thickening of skin, increased skin markings and hyperpigmentation. Increase in thickness of Stratum Spinosum/Malpighi Seen in Chronic itchy dermatoses Reference: Rooks textbook of Dermatology, 9 th edition, Chapter 4, page 13

Lichenification: Chronic, long term itching, HPE: Acanthosis Increase colour (dark) Increase thickness Increase lines Reference: Rooks textbook of Dermatology, 9 th edition, Chapter 4, page 5

Hydroquinone is the gold standard of topical treatment. It exerts its effect by inhibiting tyrosinase, the rate-limiting enzyme in melanin synthesis. HQ 2%-4% is prominently used as mono-therapy A triple combination of hydroquinone, retinoic acid, and corticosteroids (HQ 4%, tretinoin 0.05%, and fluocinolone acetonide 0.01%) Kligman regimen is commonly used Other depigmenting drugs - azelaic acid, kojic acid, glycolic acid Reference: Rooks textbook of dermatology, 9 th edition, chapter 88, page 13

Albinism - AR disorder, Tyrosinase absent Melanocytes are present in normal distribution but they fail to synthesize melanin adequately Reference: Rooks textbook of Dermatology, 9 th edition, chapter 70, page 7

Poor prognostic factors for vitiligo: Leucotrichia Lip tip variant Long standing disease Thyroid abnormalities Vitiligo on bony prominence Reference: Rooks textbook of Dermatology, 9 th edition, chapter 88, page 37