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 , eye surgery
  • 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. They are classified as infectious or noninfectious. Diagnosis is primarily clinical 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