Trichorrhexis invaginata is a distinctive hair shaft abnormality that may occur sporadically, either in normal hair or with other hair shaft abnormalities, or regularly as a marker for Nethertons syndrome. : 638 : 766–7   The primary defect appears to be abnormal keratinization of the hair shaft in the keratogenous zone, allowing for intussusception of the fully keratinized and hard distal shaft into the incompletely keratinized and soft proximal portion of the shaft. : 638

Genetics
"Bamboo hair" is a  rare autosomal recessive genodermatosis characterized by congenital ichthyosiform erythroderma, trichorrhexis invaginata, and atopic diathesis with failure to thrive. Chronic skin inflammation results in scaling and exfoliation, predisposing these patients to life-threatening infections, sepsis, and dehydration. The Netherton syndrome Mendelian Inheritance in Man is inherited as an autosomal recessive disorder due to mutations of both copies of the SPINK5 gene (localized to band 5q31-32), which encodes the serine protease inhibitor LEKTI (lymphoepithelial Kazal-type-related inhibitor). LEKTI is expressed in epithelial and mucosal surfaces and in the thymus. Each SPINK5 mutation leads to a different length of LEKTI protein, resulting in genotype/phenotype correlations in cutaneous severity, susceptibility to atopic dermatitis, growth retardation, skin infection, increased stratum corneum protease activities, and elevated kallikrein levels in the stratum corneum.Trichorrhexis invaginata, or bamboo hair, is a hair shaft abnormality that occurs as a result of an intermittent keratinizing defect of the hair cortex.
Randomization was stratified by chemotherapy choice (capecitabine, eribulin, gemcitabine, or vinorelbine), number of lines of therapy in the metastatic setting (≤ 2, > 2), and number of metastatic sites (≤ 2, > 2). The trial was conducted at 166 sites in the United States and 16 other countries.It was approved for medical use in the United States in December 2020. References
External links
"Margetuximab". Drug Information Portal. U.S. National Library of Medicine.