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Lymphomatoid papulosis

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 Lymphomatoid papulosis (LyP) is a chronic papulonodular disorder that consists of recurrent, self-healing crops of papulonodules characterized by a variable infiltrate of CD30+ lymphocytes on histopathology. In the World Health Organization/European Organization for the Research and…

Lymphogranuloma venereum

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 Lymphogranuloma venereum (LGV) is an uncommon sexually transmitted infection occurring mainly in the tropics. It is caused by one of the three serovars (L1, L2, L3) of the intracellular bacterium Chlamydia trachomatis . The incubation period…

Lymphocytoma cutis

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 Lymphocytoma cutis (cutaneous B-cell lymphoid hyperplasia, cutaneous B-cell pseudolymphoma, Spiegler–Fendt sarcoid) is an entity encompassing a spectrum of benign B-cell lymphoproliferative diseases that share clinical and histopathologic features that may mimic cutaneous low-grade B-cell lymphoma. Various…

Lymphedema

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 Lymphedema is a chronic, progressive, and debilitating condition due to abnormal accumulation of protein-rich lymphatic fluid in interstitial spaces. Lymphedema is classified into primary and secondary types. Primary lymphedema is caused by a developmental malformation of…

Lymphangioma circumscriptum

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 Lymphangioma circumscriptum (LC) is an uncommon lymphatic malformation. It presents on the skin surface as grapelike groups of thin-walled, translucent, lymph-filled vesicles, often compared with frog spawn. Hemorrhage within the lesions can create a deep red…

Lyme borreliosis

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 Lyme disease is a multisystem illness caused by spirochetes of the genus Borrelia . In North America, the causative agent is Borrelia burgdorferi , whereas in Europe, disease is caused primarily by B. afzelii and B.…

Livedoid vasculopathy

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 Livedoid vasculopathy, or livedoid vasculitis, is a painful ulcerative condition of the lower extremities with characteristic clinical and histopathologic features. Pain is a prominent feature, associated with tiny infarctive, shallow ulcerations most often involving the legs…

Livedo reticularis

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 Livedo reticularis (LR) is the netlike, mottled, violaceous discoloration of the skin secondary to dilatation and stagnation of blood within dermal capillaries. The unaffected normal-colored islands of skin are the areas where blood supply is sufficient;…

Lipodermatosclerosis

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 Lipodermatosclerosis (LDS) refers to the ‘woody’ indurated skin of the lower extremities in patients with longstanding venous disease. LDS is a form of fibrosing panniculitis that results from chronic inflammation and progressive fibrotic process of the…

Linear IgA bullous 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 Linear IgA bullous dermatosis is a clinically and immunologically heterogeneous, subepidermal autoimmune blistering disease. It is defined by pure or predominant IgA linear deposits at the epidermal basement membrane zone of skin or mucous membrane. This…

Lichen simplex chronicus

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 Lichen simplex chronicus (LSC, or neurodermatitis circumscripta) is characterized by pruritic, lichenified plaques that most often occur on the neck, anterior tibias, ankles, wrists, and anogenital region in response to chronic localized scratching or rubbing. Primary…

Lichen sclerosus

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 Lichen sclerosus (LS) is a common dermatosis that has a predilection for the ano-genital skin. It occurs in both sexes but is more common in females and has two peaks of incidence – in girls before…

Lichen planus

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 Lichen planus (LP) is a pruritic, papulosquamous disease with characteristic histopathologic and clinical features. Classically, lesions are described with the 6 ‘ P ’s: purple, pruritic, planar, polygonal, papule, and plaque. In some patients, fine white…

Lichen planopilaris

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 Lichen planopilaris (LPP), also known as follicular lichen planus , is a clinical syndrome consisting of lichen planus (LP) associated with cicatricial scalp alopecia. The condition is more common in women and presents with perifollicular erythema…

Lichen nitidus

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 Lichen nitidus is an uncommon, idiopathic condition presenting with 1- to 2-mm diameter flat-topped or domed papules. They usually remain discrete but may be grouped. They can occur on any part of the body but mainly…

Lichen myxedematosus

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 Lichen myxedematosus (LM) is a rare, chronic disease characterized by infiltration of the skin with mucin-producing fibroblasts. Typical examination findings include firm, indurated, shiny, skin-colored to erythematous papules that can coalesce into nodules and plaques. The…

Leukocytoclastic vasculitis (cutaneous small vessel vasculitis)

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 Leukocytoclastic vasculitis (LCV) is a histological term that denotes vasculitis of small vessels (capillaries and postcapillary venules). LCV is the histological presentation of cryoglobulinemic vasculitis, IgA vasculitis, normocomplementemic and hypocomplementemic urticarial vasculitis, vasculitis that may be…

Leprosy (including reactions)

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 Leprosy, or Hansen disease (HD), is an infection caused by Mycobacterium leprae , affecting the skin, respiratory mucosa, peripheral nerves, and other organs. The cardinal features are anesthetic skin lesions, enlarged peripheral nerves, and peripheral neuropathy…

Lentigo maligna

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 Lentigo maligna (LM) is a subtype of preinvasive intraepidermal melanoma (viewed by some as melanoma in situ) that classically presents as widespread pigmented patches of atypical melanocytes in the background of longstanding sun damage. The lifetime…

Leishmaniasis

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 Leishmaniasis is a flagellate protozoan disease caused by many species of the genus Leishmania. It can be classified into three clinical forms: visceral (kala azar), which is the most severe form; mucocutaneous, which may lead to…