Thin Upper Lip: Causes and Medical Significance

What a thin upper lip means

The upper lip has two parts: the vermilion, the red part, and the skin above it, which includes the philtrum, the vertical groove running from the nose to the lip. Lip fullness varies a great deal between people and families. A thin upper lip on its own, in a healthy child or adult, is a normal variation.

Doctors pay attention to it only in context. In a newborn or child, a thin upper lip is one item in a pattern of facial features that can point to a prenatal exposure or a genetic condition.

Thin upper lip and fetal alcohol syndrome

Alcohol crosses the placenta. Exposure early in pregnancy, at about the third week after conception, when the midface is forming, can alter facial development. Fetal alcohol syndrome (FAS), the most recognizable form of fetal alcohol spectrum disorders (FASD), is diagnosed with:

1. Three characteristic facial features: - a thin upper lip (vermilion) - a smooth philtrum, with the groove flattened or absent - short palpebral fissures, meaning small eye openings measured from inner to outer corner
2. Growth deficiency, before or after birth.
3. Central nervous system problems: small head size (microcephaly), structural brain differences, or problems with learning, attention, memory, behavior and coordination.

The facial features are assessed with a lip-philtrum guide, a set of photographs ranked from 1 (very full lip, deep groove) to 5 (thinnest lip, smoothest philtrum). Scores of 4 or 5 count toward the diagnosis. Separate guides exist for different ethnic backgrounds, because normal lip shape varies.

Most people with FASD do not have all the facial features. Many have the brain and behavior effects of alcohol exposure without a distinctive face, so a normal-looking face does not exclude FASD.

Other causes of a thin upper lip

Genetic and developmental syndromes

A thin upper lip is part of the facial pattern in several conditions, usually with other features such as heart defects, growth problems or developmental delay:

• Cornelia de Lange syndrome: thin upper lip with downturned corners, joined eyebrows, small hands and growth delay
• 22q11.2 deletion syndrome
• Smith-Magenis syndrome and other chromosomal conditions
• Prader-Willi syndrome (thin upper lip with almond-shaped eyes)
• Fetal anticonvulsant syndromes, such as from valproate exposure in pregnancy

Aging

With age, the lips lose collagen, fat and muscle volume, and the upper lip lengthens while the vermilion thins. This is a normal change, accelerated by sun exposure and smoking.

Other factors

• dental changes such as loss of teeth or bone, which reduce lip support
• scarring from cleft lip repair or injury

How doctors evaluate a child

If a pediatrician notices a thin upper lip along with other features, they will:

• ask about pregnancy, including alcohol, medicines and other exposures, in a supportive, non-judgmental way
• measure growth, head circumference and the eye openings
• grade the lip and philtrum with a standard guide
• assess development, learning, attention and behavior
• examine the heart, eyes, hearing, skeleton and kidneys, which can be affected in FASD and genetic syndromes
• refer to a developmental pediatrician, geneticist or specialized FASD clinic, sometimes with genetic testing to look for other causes

Support and treatment

There is no treatment that changes lip shape in FASD or genetic syndromes, and none is needed for health reasons. What matters is support for the child's development:

• early intervention and special education services
• speech, occupational and physical therapy
• behavioral therapy and parent training
• treatment of attention problems, sleep problems and mood
• a stable, nurturing home environment, which improves outcomes

For adults concerned about thin lips for cosmetic reasons, options include hyaluronic acid fillers and lip lift procedures by a qualified practitioner.

Prevention of FASD

FASD is entirely preventable. There is no known safe amount or safe time to drink alcohol during pregnancy, according to the CDC and the American Academy of Pediatrics. Anyone pregnant or trying to conceive is advised not to drink. Stopping at any point in pregnancy reduces risk.

Frequently asked questions

What does a thin upper lip mean?

Usually it means nothing medically: lip shape is inherited and lips thin with age. In a child, a thin upper lip combined with a smooth philtrum and small eye openings can be a sign of fetal alcohol syndrome, and it is part of some genetic syndromes.

Is a thin upper lip a sign of fetal alcohol syndrome?

It can be one of the signs, but not on its own. Fetal alcohol syndrome is diagnosed when a thin upper lip, smooth philtrum and short eye openings occur together with growth problems and brain or developmental effects, plus confirmed or likely alcohol exposure in pregnancy.

What is a smooth philtrum?

The philtrum is the vertical groove between the nose and the upper lip. In a smooth philtrum, the ridges on either side are flattened or absent. Along with a thin upper lip, it is a characteristic facial sign of fetal alcohol syndrome.

Can you have FASD without the facial features?

Yes. Most people with fetal alcohol spectrum disorders do not have the distinctive face. They may still have problems with learning, memory, attention, behavior and coordination. Diagnosis is based on the whole picture, not on facial appearance alone.

Why do lips get thinner with age?

Lips lose collagen, elastic fibers, fat and muscle volume over time, and the bone and teeth that support them change. Sun exposure and smoking speed this up. The upper lip also tends to lengthen, making the red part look thinner.