Collection of dermatological disorders

This learning card covers various dermatological disorders, including sebaceous and epidermoid cysts, cat scratch disease, miliaria, nummular 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
    • 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.
• 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: 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:^[13]

• 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:^[14]

• Definition: inflammatory skin disorder caused by shaving
• Epidemiology: most common in black men (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: firm, hyperpigmented, tender, pruritic papules and pustules on beard area
• 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:^[15]

• 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:^[16]