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Leiomyoma

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Cutaneous leiomyomas are rare, benign neoplasms originating from smooth muscle. Three types exist: (1) piloleiomyoma, the most common type, arising from the arrectores pilorum muscle; (2) dartoic myoma, or genital leiomyoma, arising from the scrotal/labial dartos…

Leg ulcers

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Leg ulcers are common and pose a major threat to public health and the economy due to their high prevalence, recurrence rates, cost, and their impact on patients’ quality of life. Often recalcitrant to therapy, the…

Langerhans cell histiocytosis

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Langerhans cell histiocytosis (LCH) is a rare, proliferative neoplastic condition of inflammatory cells with clonal proliferation of a subtype of epidermal dendritic cells, the Langerhans cells. It affects children about five times more frequently than adults.…

Keratosis pilaris and variants

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Keratosis pilaris (KP) is a common inherited disorder characterized by tenacious keratin plugging of follicular orifices affecting characteristic body sites. It typically presents in childhood on the extensor aspects of the upper arms, anterior surfaces of…

Keratosis lichenoides chronica

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Introduction Keratosis lichenoides chronica (KLC), also known as Nekam disease, is a rare, chronic disorder characterized by erythematous to violaceous keratotic papules and plaques arranged in a linear and reticular pattern over the trunk and extremities.…

Keratoacanthoma

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image A keratoacanthoma (KA) is a form of well-differentiated squamous cell carcinoma characterized by its low metastatic potential and capacity for spontaneous regression. Clinically, a KA appears as a rapidly growing nodule sharply circumscribed and often crateriform.…

Keloids

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Keloids are dermal hyperproliferative growths of dense fibrous tissue that extend beyond the borders of the original wound and do not regress spontaneously. In addition to the cosmetic disfigurement and negative psychological impact that keloids may…

Kawasaki disease

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Kawasaki disease (KD), seen primarily in infants and children, is an acute, febrile, multiorgan vasculitic process known for its mucocutaneous and nodal involvement. Although KD was described in Japan several decades ago, its pathogenesis has yet…

Kaposi sarcoma

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Kaposi sarcoma (KS) is a distinct, often multifocal, endothelial neoplasm etiologically linked to Kaposi sarcoma herpesvirus (KSHV) or human herpesvirus 8 (HHV8), predominantly transmitted via saliva but also by solid organ transplantation. In the United States,…

Juvenile xanthogranuloma

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image The non-Langerhans cell histiocytosis juvenile xanthogranuloma (JXG) is a benign disease common in infancy and early childhood but may affect adults as well. JXG presents as single or multiple rubbery, firm, round to oval yellow-red to…

Juvenile plantar dermatosis

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Juvenile plantar dermatosis (JPD) is a symmetrical, scaly, and fissured eruption affecting the ball of the foot, heels, and occasionally the finger pulps. The instep and interdigital skin are rarely affected. The condition occurs almost exclusively…

Jessner lymphocytic infiltrate

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Jessner lymphocytic infiltrate (JLI) is a chronic, inflammatory condition presenting with erythematous or reddish-brown papules or annular or arciform plaques, which can expand peripherally and sometimes develop central healing. The lesions are usually seen in adults…

Jellyfish stings

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Jellyfish are members of the phylum Cnidaria, which consists of five classes: Cubozoa (box jellyfish), Hydrozoa (Portuguese man-of-war and bluebottle), Scyphozoa (true jellyfish), Anthozoa (corals and sea anemones), and Staurozoa (staromedusans). They have a worldwide marine…

Irritant contact dermatitis

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Irritant contact dermatitis (ICD) is the most common form of contact dermatitis and is defined as the reaction to an exogenous substance – the irritant – that damages the epidermis through physical or chemical mechanisms, triggering…

Inducible urticarias, aquagenic pruritus, and cholinergic pruritus

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Inducible Urticarias About 25% of patients with chronic urticaria have a definable and reproducible inducing trigger that distinguishes them from those with spontaneous urticaria and urticarial vasculitis. Inducible urticarias are defined by the predominant inducing stimulus…

Impetigo

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Impetigo is a common superficial bacterial infection of the skin, caused by Staphylococcus aureus or Streptococcus pyogenes . The infection is highly contagious and can easily spread to other body sites or close contacts. Impetigo usually…

Ichthyoses

Acknowledgment We thank Dr. Mary Williams for her role in helping to edit this chapter. Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Mutations in over 50 genes cause ichthyosis, resulting in abnormal barrier function with increased transepidermal water loss (TEWL) and compensatory epidermal…

Hypopigmented disorders

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Progressive macular hypomelanosis Open full size image Hypopigmented disorders present as areas of skin that are lighter than normal due to reduced melanin. In contrast, depigmented lesions, such as those caused by vitiligo, present as milky-white patches due to complete…

Hypertrichosis and hirsutism

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Introduction Hirsutism is the excessive growth of terminal hair in women in male androgen–dependent areas (face, breasts, thighs, abdomen, back). Approximately 5–10% of women are affected worldwide with significant impacts on quality of life. The Ferriman–Gallwey…

Hyperhidrosis

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports Open full size image Hyperhidrosis is a condition characterized by abnormally increased perspiration, beyond that required for thermoregulation. It may indicate an underlying medical disorder, but more commonly it is idiopathic and results in significant deterioration in quality of life,…