Loose Anagen Syndrome (LAS)
Loose anagen syndrome (LAS) is a congenital or early-onset disorder of hair anchoring in which hairs in the growth phase (anagen) sit loosely in the follicle and can slip out easily, and painlessly, with brushing, a gentle tug or rubbing.
It is most often diagnosed in children, especially girls aged 2–6. It may be inherited in an autosomal dominant pattern with variable expressivity, or it may occur sporadically.
At the molecular level, LAS comes from a loss of adhesion between the hair shaft cuticle and the inner root sheath:
- Faulty keratinization of the inner root sheath (IRS): normally, the hair cuticle and the inner root sheath interlock through keratin hooks, holding the anagen hair firmly deep in the dermis. In LAS, the inner root sheath keratinizes abnormally early (linked to variants in the KRT71 gene or other structural protein defects), and this mechanical grip is lost.
- Anagen hairs slip out without their outer sheath: because the shaft separates from the IRS inside the follicle, a light pull draws out the growing hair without the outer root sheath.
- The "umbrella handle" root: under a light microscope, a freshly pulled anagen root is abnormally bent (bent/floppy root), has no outer sheath, and shows a wrinkled cuticle just above the root (ruffled/rumpled cuticle). This is the hallmark finding that confirms LAS.
LAS is one of the leading causes of apparent hair loss in children, yet it is often mistaken for alopecia areata or trichotillomania (compulsive hair pulling). At Haute-Derma, a hair pull test combined with on-the-spot microscopy of the hair roots can confirm LAS within minutes, sparing families unnecessary corticosteroid treatment or invasive tests.
Clinical Types and Trichoscopy Findings
LAS can look quite different from one patient to another and is divided into three main types:
- Clinical types:
- Type A (mild, diffuse thinning): sparse, fine hair that rarely grows past the shoulders because it keeps coming out with brushing or washing.
- Type B (unruly, frizzy hair): the hair is not only thin but also dry and irregularly frizzy, tangles very easily and is hard to style.
- Type C (adult loose anagen hair): less common; patients notice constant heavy shedding even though overall hair density is normal.
- Key clinical clues:
- The child's hair "never needs cutting" because it rarely grows long.
- Parents often find a lot of hair on the pillow in the morning or in the hairbrush.
- Hair pull test: the doctor grasps 40–50 hairs between the fingers and pulls gently. Normally only 1–2 telogen hairs come out. In LAS, more than 10–20 intact anagen hairs come out easily, with no pain at all.
- Trichoscopy and light microscopy:
- Light microscopy: hooked anagen roots shaped like a golf club or umbrella handle, missing the outer root sheath, with a ruffled cuticle near the root.
- Trichoscopy: empty follicles, hairs of uneven thickness, and hair shafts that exit the scalp at abnormal angles.
Management and Hair Care at Haute-Derma
LAS is benign and has an excellent outlook. Management focuses on protecting the hair, reducing friction and reassuring the family:
Natural Course and Parent Education
- Improves with age: most cases settle and improve markedly by puberty, as follicles grow larger and root more deeply and hormonal changes tighten the bond with the inner root sheath.
- Reassurance: families should know that LAS does not cause permanent baldness, does not destroy hair follicles and is not linked to any serious internal disease.
Gentle, Low-Friction Hair Care
- Minimize brushing: use a wide-tooth comb and detangle from the ends first before combing from the roots. Avoid combing while the hair is wet.
- Avoid tight hairstyles: no tight ponytails or braids pulled close to the scalp.
- Less friction during sleep: a smooth silk or satin pillowcase reduces rubbing as the child turns at night.
Supportive Medical Treatment (When Needed)
- Topical minoxidil (2–5%): although LAS is a mechanical anchoring problem, minoxidil may encourage thicker hairs and a longer anagen phase, helping hair hold on better and grow longer in children with heavy shedding.
- Nutritional support: a balanced diet with enough micronutrients, especially zinc, biotin and vitamin D, to support keratin production.
