Children may acquire M. contagiosum through skin-to-skin contact with another affected child, by sharing gymnasium equipment, or through public baths and swimming pools. Parents may report recent exposure to other children affected with M. contagiosum at school, camp, or public recreational facilities. The infection can also be transmitted by sexual contact with an affected partner. Individuals who are immunosuppressed may experience a more severe localized eruption. The infection usually resolves spontaneously by 18 months but can persist for as long as 5 years.

Complications of M. contagiosum include autoinoculation from trauma (shaving) or by manipulation of lesions by the patient. Cellulitis and secondary infections can also occur, resulting in abscess formation or necrotizing cellulitis.

Skin lesions are about 0.04 to 0.08″ (1 to 2 mm) in diameter and appear as waxy, flesh-colored, dome-shaped, umbilicated papules with a smooth surface. In children, lesions usually are distributed on the trunk, arms, legs, and face, whereas in immunocompetent adults, lesions are found on the genitalia, lower abdomen, inner upper thighs, and/or buttocks. Lesions may be few in number or numerous, depending on the patient’s immune state. Patients with human immunodeficiency virus have been known to have hundreds of systemic lesions, which are often larger than 0.8″ (2 cm) in diameter and confluent. Pruritus and perilesional eczematous reactions may also develop. The average duration of an untreated lesion is 6 to 9 months but may be as long as 5 years. M. contagiosum is rarely found in the oral mucosa or conjunctiva but may be located on the face.