Dermatology knowledge: skin tumours, inflammatory skin diseases, hair & nails, allergies

Skin tumours

Basal cell carcinoma

Basal cell carcinoma Origin: follicular/perifollicular pluripotent stem cells, Mutation of PTCH1/SMO in the Hedgehog signaling pathway or p53.

Skin tumour

Melanoma

Origin: 70% de novo, only 30% on nevi. Precursors in children: Giant Nevi or Spitz Nevi.

Skin tumour

Lentigo maligna

Definition: Lentigo maligna is a melanoma in situ on chronically sun-damaged skin; only once the basement membrane is breached is it called lentigo …

Skin tumour

Cutaneous squamous cell carcinoma

Malignant epithelial tumor originating from the keratinocytes of the epidermis.

Skin tumour

Actinic keratosis

Actinic keratosis is a chronic UV-induced dysplasia of the [keratinocytes|fibroblasts|melanocytes|endothelial cells] with potential for progression …

Skin tumour

Actinic cheilitis

Definition: actinic keratosis of the vermilion, almost exclusively of the lower lip as the main sun terrace; clinically a dry, scaling, ill-defined …

Skin tumour

Merkel cell carcinoma

Cell of origin: Merkel cells / mechanoreceptors — neuronal origin in epidermal basal layer.

Skin tumour

Microcystic adnexal carcinoma

Definition low-grade eccrine + infiltrative — sweat gland tumor on the face (cheeks, upper lip, nose) of adults.

Skin tumour

Dermatofibroma

Dermatofibroma (synonyms: benign fibrous histiocytoma, in everyday practice simply "histiocytoma") = benign fibrohistiocytic proliferation of the dermis.

Skin tumour

Cutaneous angiosarcoma

Angiosarcoma is a rare, highly malignant endothelial soft tissue sarcoma with vascular differentiation, accounting for approximately 2% of all soft …

Skin tumour

Infantile hemangioma

Tumors: Infantile hemangioma (IH), congenital hemangiomas (RICH/PICH/NICH), pyogenic granuloma, angiosarcoma — Characteristic: proliferative, …

Skin tumour

Kaposi's sarcoma

HHV-8-associated semimalignant tumor of the endothelia of blood and lymphatic vessels with optional visceral dissemination (GI tract with bleeding, …

Skin tumour

Dermatofibrosarcoma protuberans

Most common sarcoma of the skin, fibroblastic differentiation with (myo-)fibroblastic components.

Skin tumour

Mycosis fungoides

Mycosis fungoides (MF) = most common cutaneous T-cell lymphoma (CTCL), originating from CD4-positive helper memory T-cells with skin tropism.

Skin tumour

Cutaneous pseudolymphoma

Definition: benign, polyclonal lymphoreticular proliferations, difficult to distinguish from cutaneous lymphomas.

Skin tumour

Mastocytoma

Mastocytoma = benign cutaneous mast cell accumulation in the dermis with local histamine release.

Skin tumour

Porokeratosis

Clinical features: sharply demarcated, centrally atrophic lesions with a ridge-like raised border — „like a wall"; this peripheral ridge is the …

Skin tumour

Nevus sebaceus

Naevus sebaceus (Jadassohn): congenital yellow-orange hairless plaque with verrucous surface, on scalp/face, hyperplasia of sebaceous glands + …

Skin tumour

ILVEN – inflammatory linear verrucous epidermal nevus

Definition: blaschko-linear, inflammatory verrucous epidermal nevus; unlike the bland verrucous nevus it stays persistently inflamed and is …

Skin tumour

Atypical fibroxanthoma

AFX = superficial, dermally localized fibrohistiocytic neoplasm of UV-exposed skin in older patients.

Skin tumour

Pleomorphic dermal sarcoma

PDS = the "more aggressive / deeper brother" of AFX with at least one aggressive histological feature.

Skin tumour

Epithelioid sarcoma

Clinical presentation: Patients 20–40 years + distal extremities — painless nodules on hand/forearm.

Skin tumour

Extramammary Paget disease

EMPD = apocrine-differentiated intraepithelial adenocarcinoma with slow pagetoid spread in the epidermis.

Inflammatory skin diseases

Inflammatory dermatosis

Cheilitis granulomatosa (Miescher)

Cheilitis granulomatosa Miescher: chronic-recurrent, painless swelling of the lips (often upper lip), histologically non-caseating granulomas. …

Inflammatory dermatosis

Erythema annulare centrifugum (EAC)

Erythema annulare centrifugum (EAC, Darier 1916) = figurate (gyrate) erythema group with slowly centrifugal spread and border-emphasized morphology.

Inflammatory dermatosis

Erythema nodosum

Epidemiology: Women 20–40 years, self-limiting over 3–6 weeks.

Inflammatory dermatosis

Graft-versus-host disease (GvHD)

GvHD = Donor immune cells recognize recipient antigens as foreign → systemic immune reaction after allogeneic stem cell or organ transplantation due …

Inflammatory dermatosis

Granuloma annulare

Granuloma annulare (GA) = chronic-recurrent, granulomatous skin disease with annular plaques.

Inflammatory dermatosis

Cutaneous sarcoidosis

Epidemiology: F: M ≈ 2: 1, more common in Africans (in DE also German / Scandinavian population). First manifestation 20–40 years.

Inflammatory dermatosis

Lichen planus

Non-contagious acute, subacute to chronic, markedly pruritic and mostly self-limiting inflammatory disease of the skin and/or mucous membranes of …

Inflammatory dermatosis

Lichen sclerosus

Pathology & Epidemiology: collagen hypertrophy with atrophy of the epidermis and elastic fibers; anogenital (90–94% of cases) and extragenital (6–10%).

Inflammatory dermatosis

Lichenoid drug eruption

Predilection sites: Different from classic LP (e.g., trunk, extensor surfaces)

Inflammatory dermatosis

Behçet's disease

Chronic, inflammatory, relapsing generalized vasculitis with multiple organ involvement.

Inflammatory dermatosis

Grover's disease (transient acantholytic dermatosis)

Grover disease (Transient Acantholytic Dermatosis, TAD) = acquired, usually transient acantholytic dermatosis; Grover 1970 first description.

Inflammatory dermatosis

Nail psoriasis

Matrix involvement → incomplete keratinization of the nail plate with pitting or trachyonychia. Nail-bed involvement: subungual hyperkeratosis with …

Inflammatory dermatosis

Pityriasis rosea

Pityriasis rosea (PR, Gibert disease) = acute, self-limiting exanthematous dermatosis probably triggered by HHV-6 / HHV-7 reactivation (Drago 2005).

Inflammatory dermatosis

Pityriasis rubra pilaris

Pityriasis rubra pilaris (PRP) = chronic inflammatory, papulosquamous skin disease, clinically positioned between psoriasis and ichthyosis.

Inflammatory dermatosis

PLEVA (Pityriasis lichenoides et varioliformis acuta)

Definition & Clinical: Acutely appearing exanthematous lymphoproliferative T-cell disease with lichenoid, polymorphic 0.5–3 cm papules, erythema, …

Inflammatory dermatosis

Psoriasis vulgaris (plaque psoriasis)

Chronic inflammatory Th17-mediated dermatosis with histological hyperproliferation and parakeratosis of the epidermis. Characteristic is a …

Inflammatory dermatosis

Pyoderma gangrenosum

Pathogenesis: Pathogenesis involves IL-36 / IL-1β / IFN-γ (neutrophilic inflammation).

Inflammatory dermatosis

Reactive arthritis (Reiter syndrome)

Classification: seronegative spondyloarthritis, often associated with psoriasis spectrum.

Inflammatory dermatosis

Sweet syndrome (acute febrile neutrophilic dermatosis)

Triggers: Classically, infection + medications + neoplasms plus pregnancy + IBD.

Skin appendages

Hair, nails & sebaceous glands

Acne fulminans

Course & target group: Acne fulminans is the most severe variant of acne conglobata with an acute systemic inflammatory course and predominantly …

Hair, nails & sebaceous glands

Hidradenitis suppurativa (acne inversa)

Acne inversa / Hidradenitis suppurativa (HS) = chronic-recurrent inflammatory skin disease of the pilosebaceous unit in areas with apocrine sweat …

Hair, nails & sebaceous glands

Acne vulgaris

Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit, arising from seborrhea + hyperkeratosis + C. acnes. Increasingly, …

Hair, nails & sebaceous glands

Alopecia areata

AA = non-scarring, autoimmune-mediated hair loss disorder with circumscribed bald areas.

Hair, nails & sebaceous glands

Androgenetic alopecia

AGA = androgen-driven non-scarring alopecia with progressive miniaturization of terminal hairs to vellus hairs.

Hair, nails & sebaceous glands

Folliculitis (infectious)

Folliculitis simplex (Staphylococcus aureus): the commonest pathogen of bacterial folliculitis; follicularly bound erythematous papules and …

Hair, nails & sebaceous glands

Lichen planopilaris

Pathogenesis: Pathogenetically central is Th1/Th17 + CD8+ T-cells against bulge with IFN-γ apoptosis.

Hair, nails & sebaceous glands

Milia (milium)

Definition: 1–2 mm whitish-yellow, firm epidermal keratin cysts — essentially a miniature epidermal cyst.

Hair, nails & sebaceous glands

Perioral dermatitis

Perioral dermatitis (POD) = chronic-recurrent, rosaceiform dermatosis with follicular papulopustules perioral / perinasal / periocular with a free …

Hair, nails & sebaceous glands

Rosacea

Multifactorial: Dysregulation of innate immunity + neurovascular dysfunction. Cathelicidin/LL-37 ↑ → Inflammation. Demodex folliculorum as a cofactor.

Hair, nails & sebaceous glands

Telogen effluvium

Diffuse, non-scarring hair loss due to synchronous shift from anagen to telogen phase with consecutive shedding 2–4 months after trigger.

Hair, nails & sebaceous glands

Ingrown toenail (unguis incarnatus)

The lateral nail edge breaks through the nail fold — a foreign-body reaction, not a primary infection. The great toe is almost always affected. …

Hair, nails & sebaceous glands

Scarring (cicatricial) alopecias

Scarring (cicatricial) alopecia = irreversible hair follicle loss due to inflammatory destruction of the stem cell region (bulge) → follicular ostia …

Allergies

Allergy & eczema

Angioedema

Typical for angioedema is the absence of wheals. Furthermore, they often appear early at first manifestation and, especially in bradykinin-mediated …

Allergy & eczema

Atopic dermatitis (atopic eczema)

Chronic-recurrent, non-contagious inflammatory dermatosis due to barrier defect and dysregulation of the innate and adaptive immune system with Th2 …

Allergy & eczema

Mastocytosis (urticaria pigmentosa)

Mastocytosis = clonal proliferation of morphologically / immunophenotypically atypical mast cells in the skin and/or organs.

Allergy & eczema

Seborrhoeic dermatitis

Seborrheic eczema is a chronic-recurrent inflammatory dermatosis of sebaceous gland-rich areas. The pathogenesis is based on an interaction of …

Allergy & eczema

Urticaria

Acute Urticaria: < 6 weeks. Chronic Spontaneous Urticaria (CSU): ≥ 6 weeks.

Viral infections

Viral infection

Herpes zoster

Herpes zoster is caused by the reactivation of the varicella-zoster virus, a DNA virus from the family Herpesviridae. After a primary infection …

Viral infection

Mpox

Mpox (formerly monkeypox) is caused by the Mpox virus (Orthopoxvirus, double-stranded DNA virus, family Poxviridae). Two clades:

Viral infection

Erythema infectiosum (fifth disease)

Rubella (Rubella): The causative agent is the rubella virus. Symptoms are a flu-like prodrome and nuchal/retroauricular lymphadenopathy. The …

Viral infection

Varicella (chickenpox)

Primary infection with Varicella-zoster virus, double-stranded DNA virus of the family Herpesviridae.

Bacterial infections

Bacterial infection

Erysipelas

ETA and ETB are serine proteases that cleave Desmoglein-1 → intraepidermal cleavage (same mechanism as Pemphigus foliaceus).

Bacterial infection

Erythema migrans (Lyme disease)

Pathogen: Borrelia burgdorferi; in Europe also B. afzelii and B. garinii. Transmission by hard ticks (Ixodes ricinus).

Bacterial infection

Erythrasma

Typical are brownish-red, finely scaling plaques intertriginous in axilla / groin / submammary / interdigital.

Bacterial infection

Lepromatous leprosy

The pathogen is M. leprae, an acid-fast bacterium, obligate intracellular with a generation time of ~14 days — only in animal models (armadillo).

Bacterial infection

Sporotrichosis

Pathogen is Sporothrix schenckii, a dimorphic fungus with yeast/hyphae 25/37 °C — in gardeners after minor injuries from plant thorns.

Fungal infections

Fungal infection

Onychomycosis

Clinical features: thickening with onycholysis, yellow-brown discoloration, subungual hyperkeratosis — great toe nail most common.

Sexually transmitted infections

STI

Genital herpes

Method of choice: HSV PCR from a swab of the vesicle base or erosion — HSV DNA is available within hours and separates HSV-1 from HSV-2.

STI

Secondary syphilis (lues II)

Pathogen: Treponema pallidum (subsp. pallidum), obligate human-pathogenic spirochete, not culturable in vitro.

Parasitic skin diseases

Parasitosis

Demodicosis

Causative agent: Demodex folliculorum/brevis — belong to the normal skin flora, pathological with overpopulation > 5/cm².

Parasitosis

Filariasis

Causative agent: Filarial nematodes (Wuchereria, Brugia, Onchocerca, Loa loa) with Wolbachia endosymbionts as a therapeutic target.

Parasitosis

Cutaneous leishmaniasis

Third most common vector-borne disease worldwide after malaria + dengue.

Parasitosis

Cutaneous larva migrans

Causative agent: Hookworm larvae (Ancylostoma) (Ancylostoma braziliense/caninum) — dog/cat as reservoir, human as accidental host.

Parasitosis

Pediculosis capitis

Cardinal symptom: pruritus, erythema, secondary impetiginization from scratching.

Parasitosis

Caterpillar dermatitis caused by oak processionary moth (Thaumetopoea processionea)

Cause: The triggering agent is setae (urticating hairs) from caterpillars of the oak processionary moth (Thaumetopoea processionea).

Parasitosis

Crusted (Norwegian) scabies

Crusted scabies (Norwegian scabies) = extreme variant in immunosuppressed individuals (HIV, hematologic comorbidity, glucocorticoid therapy).

Parasitosis

Scabies

Pathogen: Sarcoptes scabiei var. hominis — obligate human pathogenic mite that burrows into the stratum corneum and creates tunnels.

Parasitosis

Tungiasis

Causative agent: Tunga penetrans — the gravid female sand flea burrows into the skin, swells as it produces eggs and dies after a few weeks.

Parasitosis

Cercarial dermatitis (swimmer's itch, schistosome larvae)

Causative agent: Schistosoma haematobium (Urogenital Schistosomiasis), S. mansoni / S. japonicum (Intestinal Schistosomiasis).

Drug reactions

Drug reaction

Stevens-Johnson syndrome

Definition (BSA detachment): SJS < 10 %, SJS/TEN overlap 10–30 %, TEN > 30 % of body surface area.

Environmental & photodermatoses

Environmental dermatosis

Erythema ab igne

Erythema ab igne (EAI) — chronically persistent net-like, livid, reticular hyperpigmentation pattern due to repeated prolonged sub-burning heat …

Environmental dermatosis

Miliaria Profunda

Obstruction level: distal, dermal portion of the duct (at the dermo-epidermal junction).

Environmental dermatosis

Miliaria Pustulosa

Pathogenesis: secondary bacterial superinfection of pre-existing miliaria rubra — most commonly Staphylococcus aureus / S. epidermidis within …

Environmental dermatosis

Miliaria rubra (heat rash)

Obstruction level: acrosyringium in the stratum spinosum / granulosum (epidermal portion of the duct).

Environmental dermatosis

Favre-Racouchot disease

Favre-Racouchot disease (nodular cutaneous elastosis with cysts and comedones) = a consequence of chronic UV damage: solar elastosis with numerous …

Environmental dermatosis

Phototoxic reaction

Clinical presentation: Sunburn-like erythema + bullae, sharply demarcated to exposed areas, burning.

Blistering diseases

Blistering

Bullous pemphigoid

Autoantibodies: linear deposition along the basement membrane zone of IgG and C3 in a smooth, band-like pattern against hemidesmosomes or against …

Blistering

Epidermolysis bullosa acquisita

Definition: Rare, acquired chronic autoimmune blistering dermatosis of the basement membrane.

Blistering

Paraneoplastic pemphigus

Association: Obligately occurs in the context of neoplasms, mostly B- and T-cell lymphomas or Castleman's tumor.

Blistering

Pemphigus vulgaris

Localized form: ≤ 1 cm² mucosa or ≤ 1% skin affected; no significant impairment of quality of life.

Connective tissue diseases

Connective tissue

Dermatomyositis

Etiopathogenesis: UV light, viruses or medications trigger autoantibodies (e.g., Anti-Mi2, Anti-TIF1γ) in genetically predisposed individuals. …

Connective tissue

Lupus erythematosus gesicht

Autoimmune disease with production of autoantibodies against nuclear material (dsDNA, Sm antigen, anti-SSA/SSB, ribonucleoproteins).

Connective tissue

Morphea

No systemic involvement. Variants: Plaque morphea, linear morphea (en coup de sabre), generalized morphea.

Connective tissue

Relapsing polychondritis

Relapsing polychondritis (relapsing polychondritis, RP) — rare autoimmune episodic cartilage inflammation that can affect all cartilaginous …

Connective tissue

Raynaud syndrome

Primary (idiopathic) Raynaud's phenomenon: Onset typically in young women before the age of 30; symmetric involvement of both hands, triggered by …

Hereditary skin diseases

Genodermatosis

Epidermolysis bullosa simplex

Reference: detailed in separate card "Hereditary Epidermolysis bullosa (EB)". Here are the key points.

Genodermatosis

Morbus Darier

Darier disease (Darier-White disease, Keratosis follicularis) = autosomal-dominant genodermatosis with acantholysis + dyskeratosis.

Vascular skin disorders

Angiopathy

Erythromelalgia

Definition: Paroxysmal functional vasodilation of the acra with the classic triad redness + burning pain + heat sensation, relieved by cooling.

Angiopathy

Leukocytoclastic vasculitis

Mechanism: Classic small-vessel vasculitis (leukocytoclastic vasculitis) is a type III reaction according to Coombs and Gell — an immune complex reaction.

Angiopathy

Lichen aureus

Pigmented purpuric dermatoses (PPD; purpura pigmentosa progressiva, "capillaritides") = group of chronic, benign lymphocytic capillaritides with …

Angiopathy

Superficial thrombophlebitis

Anticoagulation: For extensive SVT (> 5 cm) Fondaparinux 2.5 mg s.c. for 45 days (CALISTO study). For very extensive SVT, 5 mg over 21 days is also …

Angiopathy

Great saphenous vein varicosity

(For a table overview of compartments, see below at the end of the card)

Angiopathy

Deep vein thrombosis

Payr: Pain with flexion / pressure on the medial sole of the foot

Pigmentation disorders

Pigmentation

Vitiligo

Autoimmune disease with anti-melanocyte autoantibodies and CD8+ T-cell infiltration.

Metabolic skin disorders

Metabolic