Congenital smooth muscle hamartoma

Congenital smooth muscle hamartoma (CSMH) is a benign skin lesion that is present at birth or appears in the first few weeks of life. It is characterized by an overgrowth of mature smooth muscle fibers.

Clinical Features

The most common clinical feature of CSMH is a skin-colored or slightly pigmented patch or plaque, which can be located anywhere on the body but is most often found on the trunk or limbs. The size of the lesion can vary greatly, from a few millimeters to several centimeters in diameter. A unique characteristic of CSMH is the "pseudo-Darier sign", which is a transient increase in the size and color of the lesion when it is rubbed.

Pathogenesis

The exact cause of CSMH is unknown, but it is believed to result from an error in the development of the dermis during embryogenesis. This results in an overgrowth of mature smooth muscle fibers, which are the primary component of the lesion.

Diagnosis

The diagnosis of CSMH is typically made based on the clinical features and confirmed with a skin biopsy. Histologically, the lesion is characterized by an increase in the number of smooth muscle fibers in the dermis, which are arranged in a disorganized pattern.

Treatment

Treatment for CSMH is usually not necessary, as the lesion is benign and often regresses spontaneously. However, in some cases, the lesion may cause cosmetic concerns or discomfort, in which case it can be removed surgically.

Prognosis

The prognosis for individuals with CSMH is excellent, as the lesion is benign and does not have any malignant potential. However, it can cause cosmetic concerns or discomfort, particularly if it is located in a visible or sensitive area.

See Also

• Hamartoma
• Dermis
• Skin biopsy

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