Trichorrhexis Invaginata (Netherton Syndrome or Bamboo Hair) Workup

Updated: Sep 01, 2022
  • Author: Laura F McGevna, MD; Chief Editor: Dirk M Elston, MD  more...
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Laboratory Studies


Serum immunoglobulin E (IgE) levels can be increased, sometimes exceeding 10,000 IU/mL. [48]

Specific IgE antibodies to environmental and food allergens can be detected.

Hypereosinophilia can be present.

Other minor and inconsistent immunologic abnormalities have been reported; these abnormalities include transient neutrophil function defects, impaired cellular and immune responses, and raised complement levels (C3 and C4).

Light microscopy of the hair

Examine eyebrows or eyelashes for trichorrhexis invaginata, which appears as bamboo nodes when seen under the light microscope.

Trichorrhexis invaginata is the focal cup-and-ball hair-shaft deformity, with the invagination of the distal hair shaft (ball) into the expanded proximal hair shaft (cup) seen on scanning. This finding is described as a “golf tee” and is characteristic. [69]

Trichorrhexis invaginata may be limited to just a few hairs.  Eyebrows and eyelashes may develop trichorrhexis invaginata earlier, and the eyebrows may be the sole site of involvement; therefore, they should be the specimen of choice. [1, 70, 71] Obtain the hair specimen by clipping, because plucking fractures the hair shaft at the node, rendering microscopy difficult.

All patients have other hair-shaft defects (eg, pili torti, weathering).

Scanning electron microscopy

Electron microscopy shows trichorrhexis invaginata in 10-30% of clipped hair after age 2 years.

The hair fractures at the invaginated node, which is the weakest point in the hair shaft. Electron microscopy can be used to identify these proximal halves of invaginate nodes, which show a cuplike appearance from which the ball of the distal hair has fallen out.

Ultrastructural studies have shown a reduced number of tonofilament-keratohyaline structures, desmosomes, and distorted lamellar bodies. The stratum corneum may lose its lamellar structure. [72, 73, 74]


Other Tests

DNA testing of the SPINK5 gene makes several options possible, including prenatal diagnosis, early diagnosis via postnatal testing, and carrier detection in unaffected family members. Mutations can be identified in two thirds to three quarters of patients with clinically suspected Netherton syndrome. Genetic testing can aid in genetic counseling. Testing is available through the following organizations [75] :

  • Center for Human Genetics-Freiburg, Kohlhase Laboratory; Freiburg, Germany
  • Centogene GmbH, Rare Disease Company; Rostock, Germany
  • Instituto de Medicina Genomica, Innovagenomics; Salamanca, Spain
  • Instituto de Medicina Genomica, IMEGEN; Paterna, Spain
  • University Clinic Freiburg, Institute for Human Genetics; Freiburg, Germany


Skin biopsies may be performed. Cuperus et al recommend that erythroderma in neonates be evaluated with skin biopsy with lympho‐epithelial Kazal-type-related inhibitor staining (LEKTI). [76]


Histologic Findings

The histologic features of Netherton syndrome are not diagnostic and vary according to the type of the lesion and when the biopsy sample was obtained. Features of nonspecific dermatitis and psoriasiform hyperplasia are the most common histologic features. Hyperkeratosis is mild in comparison with other ichthyoses. Parakeratosis and an absent granular layer may occur at the spreading edge in ichthyosis linearis circumflexa. A mixed inflammatory cell infiltrate is seen in a perivascular distribution. Arico et al [77] reported increased numbers of CD1 cells similar to atopic dermatitis but also showed raised CD8 positivity rather than CD4 positivity in the dermis, unlike atopic dermatitis. Eosinophilic material (probably a glycoprotein) may accumulate within the granular or parakeratotic horny layer in ichthyosis linearis circumflexa lesions.

Similar to other severe congenital dermatoses, inflammatory changes are common in skin biopsy samples, but whether they are a primary or a secondary phenomenon is not known.