Hi, Dr. Greene, I'm hoping that you can help me find some information on the subject of hemihypertrophy. Like I told you in chat, my darling daughter Jemma was diagnosed at the age of 4 months. She is now 4 1/2 years old, and although I have found an on-line support group for it, most of the members don't know much about it either. We live in Australia and there is very little information to be found. I seem to be the one teaching Jemma's pediatrician about what little I do know. At the moment, Jemma's discrepancy is at 4 cm, but just 2 months ago it was 2 cm. Since she has been diagnosed the discrepancy has remained fairly consistent before her most recent growth spurt.
It has been a long and lonely journey for us (the doctors here don't seem to want to put me in contact with other Hemi families...if there are any), so any information gives me the backup I need to deal with this on our own. Once again thank you for taking the time for me in the chat today and I look forward to hearing from you. Take Care

Vonda, I'm so glad you asked! Most people are not aware of this medical condition. Hemihypertrophy, also called hemihyperplasia, is a greater-than-normal asymmetry between the right and left sides of the body. This difference can be in just one finger; just one limb; just the face; or an entire half of the body, including half the brain, half the tongue and the internal organs, or any variation in between. Someone with hemihypertrophy might have acne on only one side of the face. The skin is often thicker, and there may be more hair on the head, on the larger side. Rarely, children can have crossed hemihypertrophy (one leg and the opposite arm are larger than their partners).

Theories abound as to the cause of hemihypertrophy- perhaps it is increased blood flow or decreased lymph drainage, or nerve or hormone abnormalities. To date, not enough research has been conducted to choose between the theories. We don't know the cause, but we do know that hemihypertrophy is usually not inherited. People with hemihypertrophy can go on to have healthy, normal children (Genetic Counseling, 1993; 4:119--126).

Hemihypertrophy is a key warning to be on the lookout for several kinds of cancers. Sadly, hemihypertrophy is often not looked for and not diagnosed until after the cancer has been discovered.

None of us is exactly symmetric. I recall seeing a series of fascinating magazine photos of famous movie stars. The photos were made by putting together 2 right sides and 2 left sides of their faces. It was surprising how much this changed their appearances. I had not noticed the asymmetry until it was removed.

During World War II, a series of United States Army recruits was carefully measured, and only 23% were found to have legs of equal length. The average difference was a little more than 1/4 inch (American Journal of Roentgenology, 1946; 56:616--623). One of our ears is usually higher than the other. The two eyes are slightly different. Only rarely are two nipples at the same height and the same distance from the midline.

All of us are asymmetric, and where normal variation ends and hemihypertrophy begins is controversial. Nevertheless, the distinction is very important because hemihypertrophy carries real risks. A definition first proposed over 20 years ago still seems to me to be the best general guideline: hemihypertrophy is a 5% or greater difference in size or length between some aspect of the right and left sides of the body (Clinical Orthopedics, 1979; 144:198--211). This translates into a leg-length difference of about 1/2 inch for a 1-year-old, about 1 inch for a 5-year-old, and about 1-1/2 inches for an adult.

As children with hemihypertrophy grow, the discrepancy between the two sides increases, but the relative proportions between the two sides usually remains the same over the long haul. Variations are found among different children, but in most children, the discrepancy about doubles between the first and fifth birthdays, which sounds like what has happened in Jemma.

Hemihypertrophy can occur as an independent condition (isolated hemihypertrophy) or as a part of a genetic syndrome (i.e. Beckwith-Wiedemann syndrome). Isolated hemihypertrophy is thought to occur in about 1 in 86,000 people, but this number may change as there is more agreement on a definition and more people looking for it.