Two irregular blue-gray discolorations over the sacral area of a 4-week-old infant are most likely due to which etiology?

Two irregular blue-gray discolorations over the sacral area of a 4-week-old infant are most likely due to which etiology?

• A. Inflicted injury (abuse)
• B. Acrocyanosis
• C. Mongolian spots (congenital dermal melanocytosis)
• D. Cutis marmorata

Answer: (C)

The main idea is that these findings represent a benign, congenital dermal melanocytosis. Mongolian spots are flat, irregular blue-gray patches that most commonly appear on the lumbosacral area or buttocks of newborns or young infants. They arise because melanocytes fail to migrate completely to the epidermis during development and remain in the dermis. These patches are typically present at birth or noticed in the first weeks of life and tend to fade gradually over years. This pattern differs from other possibilities: cyanosis of acrovascular origin would affect the extremities and be related to circulation rather than a stable dermal lesion; cutis marmorata is a transient, lace-like mottling that occurs with cold and resolves with warming rather than a persistent blue-gray patch on the sacral area; injuries from abuse would present with different signs, timing, and distribution and are not congenital patches.

The main idea is that these findings represent a benign, congenital dermal melanocytosis. Mongolian spots are flat, irregular blue-gray patches that most commonly appear on the lumbosacral area or buttocks of newborns or young infants. They arise because melanocytes fail to migrate completely to the epidermis during development and remain in the dermis. These patches are typically present at birth or noticed in the first weeks of life and tend to fade gradually over years.

This pattern differs from other possibilities: cyanosis of acrovascular origin would affect the extremities and be related to circulation rather than a stable dermal lesion; cutis marmorata is a transient, lace-like mottling that occurs with cold and resolves with warming rather than a persistent blue-gray patch on the sacral area; injuries from abuse would present with different signs, timing, and distribution and are not congenital patches.