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ACANTHOSIS NIGRICANS (AN)

Etiology: May be due to:

  1. Heredity

  2. Endocrine disorder—most commonly associated with insulin resistance (i.e., diabetes mellitus), hyperandrogenic state, hypothyroidism

  3. Obesity

  4. Drugs—e.g., nicotinic acid, niacinamide, oral contraceptives, steroids

  5. Malignancy, usually adenocarcinoma—e.g., gastrointestinal (60% stomach), lung, breast

History: Rule out aforementioned causes.

Physical: Hyperpigmented velvety, typically symmetrical plaques predominantly on the neck, axillae, and groin.

Physical location & morphology may be similar for AN of different etiologies; hence, Hx and Px should aim to include/exclude these associated conditions.

DDx: Eczema (e.g., lichen simplex chronicus), hyperpigmented nevus (e.g., Becker, epidermal), confluent and reticulated papillomatosis of Gougerot and Carteaud

Investigations: Screen for diabetes (glycosylated Hgb) and insulin resistance (plasma insulin); consider searching for underlying malignancy in adult onset.

Management

  • Treat underlying disorder (e.g., remove tumor).

  • Cases associated with obesity and/or insulin resistance may improve with weight loss and/or metformin.

  • Management is difficult and mostly for cosmetic purposes.

  • Tx options: Topical tretinoin, ammonium lactate, laser therapy, dermabrasion.

ACNE VULGARIS

Inflammatory disorder of pilosebaceous follicles with a 90% prevalence in adolescence and young adulthood.

Etiology: Abnormal follicular keratinization, increased sebum 2° to androgens, Propionibacterium acnes (bacteria), inflammation. Genetic factors; occlusive cosmetic agents; medications: steroids, ACTH, androgens, danazol, iodides, lithium, antiepileptics, oral contraceptives; diseases: congenital adrenal hyperplasia (CAH), polycystic ovarian syndrome (PCOS); worse with emotional stress.

History: Often asymptomatic lesions (especially comedones), although can be tender (nodules).

Physical: Two types of lesions, predominantly affect face, neck, chest and back.

  1. Noninflammatory—open (“black heads”) and closed (“white heads”) comedones.

  2. Inflammatory—papules, pustules, cysts, nodules; deep lesions leave scars, inflammatory papules, pustules & nodules on back and check with early scarring.

DDx: Folliculitis, perioral dermatitis, rosacea

Investigations: If irregular periods, hirsutism, virilization, or not responding to conventional therapy, work-up to rule out virilizing tumor or PCOS.

Management

Treatment Options Based on Acne Type

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Treatment

Comedonal

Inflammatory

Nodulocystic

Topical Therapy

Salicylic acid

X

Retinoids

X

X

Azelaic acid

X

X

Benzoyl peroxide

X

X

Antibiotics

X

X

Systemic Therapy

Oral contraceptives

X

X

X

Antibiotics

X

X

Isotretinoin

X

X

X

Selected Topical Medications for the Treatment of Acne

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Medication

Dosage

Side Effects

Retinoids*

Adapalene (Differin)

Qhs–bid

Same as tretinoin but less severe

Tazarotene (Tazorac)

Qhs

Same as tretinoin but more severe

Tretinoin (Retin-A)

Qhs

Dryness, scaling, erythema, burning, irritation, and photosensitivity

...

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