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Question:

A 65-year-old man comes to the office due to a skin condition.  For the last 6 years, the patient has had slowly progressive, patchy depigmentation involving the face, posterior scalp, hands, genital area, and feet.  There is no associated itching, pain, or scaling.  Medical history is notable for hypertension, stable coronary artery disease, rheumatoid arthritis, and benign prostatic hyperplasia.  The patient quit smoking 20 years ago and does not use alcohol or illicit drugs.  Temperature is 36.9 C (98.4 F), blood pressure is 136/88 mm Hg, and pulse is 76/min.  Skin examination shows widespread areas of depigmentation as shown below.  Physical examination is otherwise unremarkable.

Which of the following best explains the pathology of this patient's condition?

 
Answers:

A. Age-related depigmentation

Correct answer:

B. Destruction of melanocytes

Your reply:

C. Inherited abscence of melanocytes

D. Mycobacterial infection

E. Post-inflammatory change

Explanation:

(Choices A)  Idiopathic guttate hypomelanosis is a common finding with aging and is characterized by small macules in sun-exposed areas.  

 

Explanation 

 

This patient has well-demarcated depigmented macules consistent with vitiligo.  Vitiligo is caused by regional destruction of melanocytes, most likely due to an autoimmune etiology.  Genetic and environmental factors may also play a role.  It can occur as an isolated disorder but is often associated with other autoimmune conditions (eg, autoimmune thyroid disease, rheumatoid arthritis, pernicious anemia, primary adrenal insufficiency).  The course is highly variable, although the condition is usually slowly progressive.

The diagnosis of vitiligo is usually made on clinical grounds.  Biopsy can be considered in uncertain cases and will show loss of melanocytes, often with scattered lymphocytes at the lesion border.  When treatment is desired, topical or systemic corticosteroids are the most common first-line intervention.

Educational objective: Vitiligo is caused by regional destruction of melanocytes, most likely due to an autoimmune etiology.  It is often associated with other autoimmune conditions and is usually slowly progressive.  The diagnosis is made on clinical grounds, and topical or systemic corticosteroids are the most common first-line intervention.

 

(Choice C)  Piebaldism is an autosomal dominant disorder characterized by patchy absence of melanocytes.  It is usually noticed at birth and is confined to the head and trunk.

 

(Choices D)   Infection with Mycobacterium leprae causes leprosy, characterized by areas of hypopigmentation with anesthesia.  T

 

(Choices  E) Post-inflammatory hypopigmentation is characterized by patchy involvement in areas of prior trauma or inflammation.  The lesions in these disorders are hypopigmented rather than completely depigmented, as in vitiligo.

 
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