Collection of dermatological disorders

This article covers various dermatological disorders, including sebaceous and epidermoid cysts, cat scratch disease, cutaneous mastocytosis, miliaria, nummular eczema, angiokeratoma, dyshidrotic eczema, livedo reticularis, xeroderma pigmentosum, pseudofolliculitis barbae, and albinism.

• Definition: benign, self-limiting infectious disease that is transmitted mainly by cats (via scratching, biting, or licking)
• Pathogen: Bartonella henselae (gram-negative bacillus, aerobic)
• Epidemiology: predominantly affects children and adolescents
• Clinical features
  • General: malaise, loss of appetite, fever
  • Localized
    • One or more 5–10 mm large, erythematous, non-tender cutaneous papules or vesicles develop approx. 4–6 days after exposure (in > 50% of cases) at the site of inoculation.
    • Swollen, tender lymph nodes 1–3 weeks following exposure
      • Develops as primary lesions disappear
      • Usually unilateral, occasionally suppurative
      • Most commonly involves lymph nodes of axillae, neck, or groin (nearest the site of inoculation)
      • Resolves after 2–4 months
  • In immunocompromised individuals (e.g., patients with HIV)
    • Bacillary angiomatosis
    • Hepatic peliosis
    • Bacteremia and endocarditis
• Diagnosis
  • Bacterial culture from blood, swabs, or lymph node aspirate
  • Antibody testing
  • Histological study
    • Warthin-Starry staining of the involved lymph node may show clusters of rod-shaped bacteria.
    • H&E staining of cutaneous lesions may show necrotizing granuloma formation and neutrophilic infiltrates.
• Differential diagnosis: Kaposi sarcoma (has lymphocytic infiltrate as opposed to bacillary angiomatosis)
• Treatment
  • Mild or moderate cases: azithromycin (5-day course) to decrease lymphadenopathy and the duration of illness
  • Persistent and/or disseminated cases (e.g., bacillary angiomatosis): erythromycin (or doxycycline); in case of CNS involvement or endocarditis, rifampicin should be used in combination with one of these drugs.

References:^{[5][6][7][8][9]}

• Definition: benign ectasia of the superficial dermal blood vessels with characteristic hyperkeratosis of the papillary dermis
• Clinical features
  • Asymptomatic papules, plaques, or verrucous skin lesions
    • Red, blue, or black in color
    • Usually solitary; less commonly diffuse
    • Most commonly located on the lower extremities and groin
  • Associated with Fabry disease: multiple skin lesions located on the trunk
• Diagnosis
  • Usually a clinical diagnosis
  • Skin biopsy: telangiectasia, acanthosis, hyperkeratosis
• Treatment: laser ablation, mainly a cosmetic procedure

References:^[14]

Definition: a vascular syndrome that can be caused by either benign autonomic dysregulation of cutaneous perfusion or pathological obstruction of blood vessels

Physiological livedo

• Pathophysiology: autonomic dysregulation; (functional disturbance) causing slowed cutaneous perfusion in response to external factors (i.e., cold)
• Epidemiology: incidence highest in young women
• Clinical findings
  • Symmetrical; livedo reticularis (regular, small, round) on the extremities and sometimes the trunk
  • Triggered by cold, regresses after application of warmth
• Treatment: warmth, sauna, alternating cold and warm baths
• Prognosis: improves with age

Pathological livedo

• Pathophysiology: localized obstructions slow the blood flow (organic disturbance)
• Etiology: vascular diseases (cholesterol embolism, atherosclerosis, vasculitis)
• Clinical findings
  • Irregular; , unusual livedo reticularis of the extremities and sometimes trunk
  • Persists after warming the skin
• Treatment: treat the underlying disease

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

References:^[15]

• Definition: rare, autosomal-recessive, hereditary skin disease caused by defective DNA repair mechanisms (i.e., nucleotide excision repair); in affected individuals, minimal UV radiation can lead to severe skin damage and has carcinogenic effects
• Clinical findings
  • Extreme sensitivity to light with pigmentary changes
  • Development of multiple precancerous lesions; (actinic keratoses) and eventually malignant skin cancer; (basal cell carcinoma, spinocellular carcinoma, melanoma) already in early childhood
• Management
  • Protection from light and avoidance of sun exposure
  • Frequent skin cancer screening, retinoids as prophylaxis
• Prognosis: severely limited life expectancy

References:^[16]

• Definition: inflammatory skin reaction in response to short hair that becomes entrapped within the skin
• Etiology
  • Usually occurs due to shaving (also known as razor bumps)
  • Most common in African American men because the hair shafts typically form tight coils
• Pathophysiology
  • Extrafollicular penetration: Hair enters the interfollicular epidermis after it exits the follicular orifice.
  • Transfollicular penetration: Hair penetrates the dermis before exiting the follicular orifice.
• Clinical findings
  • Lesions: firm, hyperpigmented, tender, pruritic papules and pustules
  • Location: beard region (i.e., cheeks, jaw, and neck)
• Diagnosis: clinical appearance
• Treatment
  • Cessation of shaving; alternative hair-removal techniques (e.g., laser hair removal)
  • Adjunctive: topical treatments (e.g., retinoids, corticosteroids, antimicrobials)

References:^[17]

• Definition: : congenital disorders of melanin synthesis resulting in hypopigmentation
• 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.
  • Oculocutaneous albinism (OCA): absence of melanin in the skin, hair, and the visual system
    • May be associated with Chédiak-Higashi syndrome
• Pathophysiology: impaired melanin production
  • Due to dysfunctional tyrosinase activity, or impaired transport of tyrosine or melanin
  • Normal melanocyte levels, decreased or absent melanin production
• Clinical features
  • Eyes
    • Translucent, hypopigmented blue, grey, or green irides
    • Photophobia, decreased visual acuity
    • Strabismus, nystagmus, amblyopia
    • Abnormalities of the optic nerve
  • 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

References:^[18]

• Definition: a congenital pigmentation disorder due to abnormal migration of melanocytes during embryogenesis
• Etiology: 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 palate
  • Neural tube defects
  • Associated with Hirschsprung disease
• Treatment: only supportive treatment, no curative treatment available

References:^[19]