Collection of dermatological disorders

This article covers various dermatological disorders, including cutaneous mastocytosis, miliaria, dyshidrotic eczema, livedo reticularis, and albinism.

• Definition: transient, papular exanthem following exposure to heat
• Etiology: blockage of the eccrine sweat ducts in hot and/or humid environments
• Localization: : mainly on the trunk, neck, and intertriginous areas
• Treatment
  • General measures to reduce sweating: wearing light, breathable fabrics, keeping the patient in a cool environment, removing occlusive bandages, etc.
  • Topical steroids; (hydrocortisone, triamcinolone), topical antibiotics for pustular eruptions (clindamycin, erythromycin)

• Definition: maculopapular exanthem associated with viral infections, especially hepatitis B and Epstein-Barr virus (EBV)
• Epidemiology: age of onset is < 5 years ^[2]
• Clinical features
  • Affects the face, buttocks, and extensor surfaces of the extremities
  • Pruritus may occur
  • Self-limiting, lasting between 10 days and 6 months ^[3]
• Treatment: symptomatic

• Definition: a condition characterized by a recurrent, acute blistering eczema of the palms and/or soles
• Etiology
  • Unknown (believed to be multifactorial)
  • Risk factors include:
    • Atopic dermatitis
    • Irritant contact dermatitis
    • Allergic contact dermatitis (e.g., nickel, cobalt, balsam of Peru, perfumes)
    • Dermatophyte infections
• Clinical features
  • Acute, recurrent episodes of pruritic vesicular/bullous eruptions on the palms, lateral aspects of the fingers, and/or soles
    • Warm weather exacerbates symptoms.
    • The lesions are usually multiple and deep-seated.
  • Severe cases include dystrophic nail changes (e.g., color changes, ridge formation)
• Diagnostics
  • Usually a clinical diagnosis.
  • Skin biopsy
    • To rule out differential diagnoses (e.g., psoriasis) or in case of poor response to treatment.
    • Findings include intraepidermal spongiotic vesicles/bullae without involvement of the eccrine sweat glands.
• Treatment
  • Avoid triggers (e.g., allergens and irritants such as metals, perfumes, or cigarette smoking)
  • Appropriate skin care (i.e., wash hands with lukewarm water and soap-free cleanser, apply emollients after drying hands adequately)
  • Topical corticosteroids for mild cases that do not respond to general measures
  • Oral corticosteroids for severe cases
  • Consider adding PUVA or UVA treatment for patients with refractory disease.
• Complications
  • Chronic hand dermatitis: lichenification, scaling, fissured patches and plaques
  • Secondary infection (e.g., Staphylococcus aureus)

• Description: reticular erythema with telangiectasias
• Etiology: paralysis of the deep vascular plexus of the skin caused due to chronic heat application (e.g., infrared radiation, hot water bottles)
• Pathophysiology: direct skin application of heat for extended periods of time → direct heat triggers increased melanin production → marbled, brownish hyperpigmentation
• Treatment ^[4]
  • Discontinue offending heat source
  • The condition usually resolves within months to years,
  • Permanent hyperpigmentation or scarring may occur: can be treated with topical tretinoin or hydroquinone
  • Topical 5-fluorouracil in the case of epithelial atypia
• Complications ^[4]
  • Squamous cell carcinoma
  • Merkel cell carcinoma: a rare, rapidly progressive neuroendocrine neoplasm that typically manifests as a painless, firm, nontender, red-blue nodule on the head or neck

• Definition: superficial bacterial skin infection with pit-like corneal defects on the soles of the feet accompanied by malodor and a burning sensation
• Epidemiology
  • Occurs worldwide (especially in athletes, industrial workers, and soldiers)
  • Risk factors include:
    • Hot, humid weather
    • Occlusive footwear
    • Hyperhidrosis
• Etiology
  • Caused by maceration and various bacteria
  • Most often occurs in association with insufficiently breathable footwear
• Clinical features: bilateral and multifocal cerebriform skin maceration and superficial erosions
• Treatment ^[5]
  • Regular changing of footwear and socks
  • Topical antibiotics (e.g., erythromycin, clindamycin)
  • Possibly botulinum toxin or iontophoresis to reduce local sweating

• Description: localized degeneration of subcutaneous adipose tissue
• Etiology: iatrogenic (secondary to subcutaneous injections), certain drugs (e.g., ARVT), pressure-induced, or idiopathic
• Treatment: depends on the underlying cause

• Description: a rheumatological, spondylarthritic disease with simultaneous occurrence of synovitis, acne, pustulosis, hyperostosis, and osteitis
• Clinical features
  • Skin: acne, palmoplantar pustulosis
  • Musculoskeletal: synovitis, hyperostosis (particularly of the sternoclavicular joint, spine, and/or pelvis), and chronic recurrent osteitis
• Etiology: unknown
• Diagnostics
  • Mainly a clinical diagnosis
  • Imaging
    • X-ray: evidence of hyperostosis
    • Scintigraphy: enhancement in affected bones and joints
    • MRI: visible inflammatory reaction (osteitis)
• Treatment: primarily symptomatic

Livedo reticularis that does not regress after application of warmth is indicative of an underlying vascular disease and requires treatment.

• Definition: : congenital disorders of melanin synthesis resulting in hypopigmentation
  • Partial albinism: a genetic condition characterized by the partial absence of melanin pigment from melanosomes in the body due to defects in the biosynthesis of melanin
  • Total albinism: a genetic condition characterized by the total absence of melanin pigment from melanosomes in the body due to defects in the biosynthesis of melanin
• Epidemiology
  • Affects all races and both sexes
  • Most types of albinism are congenital and noticed early in life (e.g., newborns).
• Classification
  • Ocular albinism (OA): Only the visual system (e.g., iris, retina) is affected, but not the skin or hair.
  • Oculocutaneous albinism (OCA)
    • Absence of melanin in the skin, hair, and iris
    • May be associated with Chédiak-Higashi syndrome
• Pathophysiology: dysfunctional tyrosinase activity or impaired transport of tyrosine and/or melanin → decreased or absent melanin production (melanocyte levels are normal)
• Clinical features
  • Eyes
    • Translucent, hypopigmented blue, gray, or green irises
    • Photophobia, decreased visual acuity
    • Strabismus, nystagmus, amblyopia
    • Abnormalities of the optic nerve (e.g., hypoplasia, abnormal crossing of optic fibers at the optic chiasm)
  • Skin and hair: milky white color, photosensitivity, sunburns
  • Associated with increased risk of skin cancer
• Treatment: only supportive treatment, no curative treatment available
  • Treatment of strabismus: eye-patching
  • Avoidance of direct exposure to UV light and regular screening for skin cancer
  • Wearing (prescription) sunglasses
  • Nitisinone : used for the treatment of hereditary tyrosinemia type 1

• Definition: a congenital pigmentation disorder due to abnormal migration of melanocytes during embryogenesis
• Etiology: an autosomal dominant inherited disorder
• Clinical features
  • Patchy depigmentation of the hair and skin (e.g., poliosis)
  • Pale blue eyes or heterochromia iridum
  • Broad nasal root
  • Congenital hearing loss
  • Cleft lip and cleft palate
  • Neural tube defects
  • Associated with Hirschsprung disease
• Treatment: only supportive treatment, no curative treatment available

• Definition: a rare, very aggressive vascular malignancy, arising from endothelial cells of blood or lymphatic vessels ^[7]
• Epidemiology: peak incidence age > 70 years ^[7]
• Etiology ^[7]
  • Radiation (e.g., radiation therapy)
  • Chronic lymphedema: especially in postmastectomy lymph node resection
  • Chemicals: Vinyl chloride and arsenic are implicated in hepatic angiosarcoma.
• Clinical features ^[8][9]
  • Location
    • More common in sun-exposed areas
    • Usually occur on the head, neck, and breast
    • May involve the internal organs (e.g., hepatic angiosarcoma)
  • Lesion
    • Blue/purple-colored with a bruise-like appearance
    • Later stage: hemorrhage or ulceration
    • High variability in appearance
• Treatment ^[9]
  • Complete resection with wide margins
  • Resection may be complicated by the aggressive course of the disease and delayed diagnosis.

• Definition: skin reactions associated with the needle trauma caused by tattooing or the inks involved
• Types
  • Infection transmitted by needle or acquired after tattooing through damaged skin (e.g., impetigo, erysipelas)
  • Eczematous hypersensitivity reactions to tattoo ink (e.g., allergic contact dermatitis, photoallergic dermatitis)
  • New skin disease (e.g., psoriasis, eczema, vitiligo)
  • MRI burn due to tattoo ink containing metals (e.g., mercury, iron)
  • Skin cancer due to carcinogenic substances in tattooing ink
• Clinical features, diagnosis, and treatment: according to diagnosis and symptoms (e.g., antibiotic treatment of erysipelas)

• Definition: a condition of localized or generalized excessive sweating
• Epidemiology: estimated to affect ∼ 5% in the US ^[10]
• Etiology
  • Primary focal hyperhidrosis
  • Secondary hyperhidrosis (e.g., due to hyperthyroidism, malignancy, obesity, or adverse effects of medication)
• Clinical features: excessive sweating that interferes with activities of daily living, frequent skin infections (e.g., tinea pedis)
  • Primary focal hyperhidrosis
    • Usually localized (e.g., underarms, forehead)
    • Both sides of the body are affected.
    • No sweating during sleep; sweating begins immediately after waking up.
  • Secondary hyperhidrosis: generalized, may occur during sleep
• Diagnostics: clinical diagnosis
• Treatment
  • Antiperspirants (over-the-counter or prescription)
  • Iontophoresis
  • Anticholinergics
  • Botulinum toxin injections
  • Surgery (surgical removal of sweat glands or sympathectomy)

• Definition: An iatrogenic skin lesion caused by accidental injection of a drug into an artery ^[11][13][14]
• Pathophysiology: embolic vessel occlusion and reflexive vasospasm → skin necrosis
• Symptoms
  • Local pain right after injection
  • Skin induration and reddening within hours following an injection
  • Purplish livedoid erythema with necrosis within days following an injection
• Treatment
  • No specific treatment exists.
  • In small lesions, conservative treatment with analgesics, topical antibiotics, and glucocorticoids can be used.
  • In extensive lesions, surgical debridement can be required.

Cutaneous granulomas are a group of conditions characterized by a chronic inflammatory skin response to a variety of stimuli, including metabolites, foreign bodies, and infection. For more information on the etiology, pathophysiology, and pathology of these conditions, see “Granulomatous inflammation.” ^[15]

Noninfectious cutaneous granulomas

Noninfectious cutaneous granulomas are often manifestations of systemic diseases, including diabetes, rheumatoid arthritis, and sarcoidosis.

Granuloma annulare

• Definition: a benign, palpable, ring-shaped nodule of unclear etiology that most commonly manifests on the extremities (especially the dorsal hands and feet)
• Epidemiology ^[16]
  • ♀ > ♂ (3:1)
  • Peak incidence: 55–60 years of age
• Classification ^[17]
  • Localized
  • Generalized (sparing the head, neck, palms, and soles)
• Clinical features
  • Varies from skin-colored to violaceous
  • Lesions may appear hypopigmented or hyperpigmented in darker skin tones.
  • Pruritus (associated with generalized granuloma annulare)
• Differential diagnosis: See “Overview of annular skin lesions” for details.
• Treatment
  • Localized disease typically resolves without treatment; treatment is recommended according to patient preferences for cosmetic reasons, in persistent pruritus, or if prognosis is uncertain.
  • Generalized granuloma annulare is more likely than localized lesions to require systemic therapy.
  • First-line: topical corticosteroids (e.g., clobetasol propionate)
  • Alternatives: intralesional corticosteroid injection (e.g., triamcinolone acetonide), calcineurin inhibitors (e.g., tacrolimus ointment), systemic steroid-sparing therapy (e.g., hydroxychloroquine, isotretinoin)
• Prognosis ^[18]
  • Localized: self-limiting
  • Generalized: chronic or relapsing

Necrobiosis lipoidica ^[19]

• Definition: a rare, chronic granulomatous disease of the skin associated with diabetes mellitus
• Epidemiology ^[20]
  • Approx. 60% of patients with necrobiosis lipoidica have diabetes mellitus.
  • ♀ > ♂
• Clinical features
  • Usually asymptomatic
  • Common sites: pretibial region
  • Initially, a reddish-brown papule that progresses to a yellow-brown papule or plaque with visible telangiectasias
  • Ulceration of the lesion may also occur following minor trauma
• Histopathology: necrobiotic palisading granuloma
  • Lymphohistiocytic infiltration with plasma cells, foam cells, and giant cells
  • Wall thickening and occlusion of small blood vessels
  • Destruction of collagen fibers in the entire corium
• Treatment: Corticosteroids may be effective (e.g., intralesional corticosteroid injections)

Rheumatoid nodules

• Definition: inflammatory cutaneous or subcutaneous lesions found primarily at pressure points (e.g., extensor side of the forearm, bony prominences)
• Epidemiology ^[20]
  • Most common extraarticular manifestation of rheumatoid arthritis (RA)
  • Associated with seropositive rheumatoid arthritis and more severe joint involvement than in individuals with no nodules ^[21]
• Clinical features: nontender, firm, subcutaneous nodules
• Histopathology: central necrosis with surrounding palisading histiocytes and granulomatous tissue ^[20]
• Treatment: intralesional corticosteroid injection or excision only required if the nodule causes pain or impairs movement
• For more information, see “Rheumatoid arthritis.”

Lupus pernio

• Definition: a pathognomonic manifestation of cutaneous sarcoidosis appearing as violaceous plaques on areas commonly exposed to cold (e.g., nose, cheeks, ears)
• Associations ^[15]
  • Sarcoidosis of the lungs (approx. 75%)
  • Sarcoidosis of the upper respiratory tract (approx. 50%)
• Clinical features
  • Extensive, indurated plaques that tend to scar
  • Distribution similar to the butterfly rash seen in systemic lupus erythematosus
• Treatment ^[22]
  • First-line: intralesional corticosteroid injection (e.g., triamcinolone acetonide)
  • Second-line: systemic glucocorticosteroids (e.g., prednisolone), steroid-sparing therapy (e.g., antimalarials, methotrexate, tetracycline)

Foreign body granulomas

• Definition: noncaseating granulomatous inflammation of the cutaneous or subcutaneous tissues in response to the introduction of foreign materials
• Classification ^[23]
  • Endogenous: due to endogenous material (e.g., hair fragments, cholesterol crystals, calcifications) identified by the immune system as foreign
  • Exogenous: due to introduction of exogenous material (e.g., cosmetic fillers, sutures, fish spines)
• Stages
  • Stage 1: formation of papule, nodule, or erythematous plaque
  • Stage 2: fibrosis and granuloma formation
• Diagnostics: ultrasound, biopsy ^[24]

Infectious cutaneous granulomas

• Definition: any granuloma caused by a pathogen
• Examples
  • Cutaneous tuberculosis: granulomatous inflammation with caseous necrosis caused by Mycobacterium tuberculosis
  • Tuberculoid leprosy: hyperesthetic, hairless, skin lesions caused by Mycobacterium leprae
  • Cutaneous leishmaniasis: the most common form of leishmaniasis, characterized by reddish macules and papules that may progress to ulcers