Health care providers do not know the exact cause of HMI, but they believe it may involve a genetic condition called mosaicism. It is twice as common in girls as in boys.

Skin symptoms are most often visible by the time a child is about 2 years old.

Other symptoms develop as the child grows, and may include:

• Crossed eyes (strabismus)
• Hearing problems
• Increased body hair (hirsutism)
• Scoliosis
• Seizures
• Streaked, whorled or mottled patches of skin on the arms, legs, and middle of the body
• Intellectual disability, including autism spectrum disorder and learning disability
• Mouth or tooth problems

Ultraviolet light (Wood lamp) examination of the skin lesions may help confirm the diagnosis.

Tests that may be done include any of the following:

• CT or MRI scan of the head for a child with seizures and nervous system symptoms
• X-rays for a child with skeletal problems
• EEG to measure the electrical activity of the brain in a child with seizures
• Genetic testing

There is no treatment for the skin patches. Cosmetics or clothing may be used to cover the patches. Seizures, scoliosis, and other problems are treated as needed.

The outlook depends on the type and severity of symptoms that develop. In most cases, skin color eventually turns to normal.

Problems that may result from HMI include:

• Discomfort and walking problems due to scoliosis
• Emotional distress, related to the physical appearance
• Intellectual disability
• Injury from seizures

Contact your provider if your child has an unusual pattern of the color of the skin. However, any unusual patterns are likely to have another cause than HMI.

Incontinentia pigmenti achromians; HMI; Ito hypomelanosis

Joyce JC. Hypopigmented lesions. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 672.

Patterson JW. Disorders of pigmentation. In: Patterson JW, ed. Weedon's Skin Pathology. 5th ed. Philadelphia, PA: Elsevier; 2021:chap 11.

Updated by: Ramin Fathi, MD, FAAD, Director, Phoenix Surgical Dermatology Group, Phoenix, AZ. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.