Hyperpigmentation caused by hyperthyroidism: differences from the pigmentation of Addison's disease.

Area of Science:

• Endocrinology
• Dermatology
• Pathology

Background:

• Hyperthyroidism is an endocrine disorder with various clinical manifestations.
• Skin changes can occur in hyperthyroidism, but specific patterns of hyperpigmentation are not well-defined.
• Distinguishing hyperthyroid-associated pigmentation from other conditions like Addison's disease is clinically relevant.

Observation:

• Two patients with hyperthyroidism presented with significant hyperpigmentation.
• The hyperpigmentation was predominantly observed on the lower extremities, including shins, feet, and nail beds.
• Histological examination revealed basal melanosis and substantial haemosiderin deposition around dermal capillaries and sweat glands.

Findings:

• The observed hyperpigmentation in hyperthyroidism cases showed a characteristic distribution on the lower extremities.
• Histopathology confirmed basal melanosis and haemosiderin deposition, indicating a specific pigmentary process.
• Treatment with mercazol, an antithyroid medication, did not lead to significant reduction in pigmentation.

Implications:

• The distinct pattern of lower extremity hyperpigmentation and haemosiderin deposition may serve as a clinical marker for hyperthyroidism.
• The poor response to treatment suggests that the pigmentation mechanism in hyperthyroidism differs from other causes.
• Further research is warranted to elucidate the pathophysiology and diagnostic utility of this specific hyperpigmentation in hyperthyroidism.