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Pediatric Hair Disorders
An Atlas and Text, Third Edition
Juan Ferrando, Ramon Grimalt
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eBook - ePub
Pediatric Hair Disorders
An Atlas and Text, Third Edition
Juan Ferrando, Ramon Grimalt
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Hair problems in child patients present a particular problem for clinicians: dermatologists, pediatricians, and family physicians can all worry they may not be up to date with what may be happening in the other specialties potentially involved. Written by authors with an international reputation, the new third edition of Pediatric Hair Disorders is full of clinical pictures, with a clear and concise text to help with the diagnosis of each entity. It will be helpful for all clinicians in training and in practice needing a quick and very visual resource to help with clinical diagnosis and to be confident they are using the best recommended techniques.
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Informations
1
Hair Shaft Dysplasias
Hair shaft dysplasias are malformations of hair shafts. Most cases are congenital, hereditary or not; others are acquired (e.g., bubble hair). The malformations may involve a localized or generalized defect, but always follow a characteristic morphologic pattern [1,2]. The defects may be restricted to the hair or even constitute a diagnostic clue pointing to a genodermatosis (e.g., Netherton syndrome, trichothiodystrophy). Classification of hair shaft dysplasias is difficult but for practical purposes we accept the scheme shown in Table 1.1 [2,3].
Monilethrix (Beaded Hair)
Monilethrix is an autosomal dominant (AD) defect of the hair shaft characterized by short hair, only a few millimeters long and beaded. Breaking of the hair shaft occurs as soon as hair emerges from the ostium folliculorum due to narrowing of the shaft segments. Focal follicular hyperkeratosis and marked hypotrichosis may also be seen. Monilethrix generally affects individuals of different generations of the same family. The morphological defect is the periodic narrowing of the hair shaft that may be seen deep in hair follicles in biopsy specimens [4,5].
Genetics: Monilethrix is an AD hereditary defect caused by mutation of genes hHb1, hHb3, and hHb6 localized on chromosome (cr) 12q13 that encode diverse trichokeratins. We have recently reported a new family with a change in the nucleotide in heterozygosis at position 154 of exon1 of gene KRT81 (154 G > C). In the DNA sequence, this substitution involves a change of one amino acid in a protein (glycine for arginine at position 52) [6]. Interruption of keratin synthesis may be the cause of periodic variations of hair shaft diameter. Autosomal recessive (AR) cases have also been reported and are due to a gene mutation (18q) that encodes desmoglein 4 (DSG4), a situation that affects affinity for plakoglobin and alters hair shaft desmosomes [7].
Clinical diagnosis: The clinical picture includes diffuse hypotrichosis and short, fragile, and beaded hairs. Localized (occipital region) or generalized marked follicular hyperkeratosis may also be seen (Figure 1.1).
Optical microscopy: Alternating periodical beading (defect) and knots (normal hair shaft diameter) are characteristic aspects that may also be seen in dermoscopy (Figure 1.2). The hair shaft diameter is normal in the beaded segment of the hair shaft and the medulla is observed; these are not seen in the narrowed segments.
Scanning electron microscopy: Microscopic images are similar to those observed in optical microscopy; hair shaft fracture is evidenced in narrowed segments.
Trichoscopy: Dermoscopy is a useful tool for diagnosing hair shaft dysplasias. The typical âpearl necklaceâ image shows elliptical beading, regularly separated by narrowing segments where hair shaft fractures are usually observed. These findings are easily identified by dermoscopyâa simple method for a quick diagnosis [8,9] (Figure 1.3).
Histology: Intrafollicular hair shaft narrowing is observed.
Dysplasias with Hair Fragility | Dysplasias with Little or No Hair Fragility |
Monilethrix | Pili annulati |
Pseudomonilethrix | Pseudopili annulati |
Pili torti | Diffuse woolly hair |
Menkes syndrome (kinky hair) | Woolly hair nevus |
Trichorrexis invaginata (Netherton syndrome) | Acquired progressive kinking |
Trichothiodystrophy | Diffuse partial woolly hair |
Trichonodosis | Acquired partial curly hair |
Distal trichorrhexis nodosa | Straight hair nevus |
Proximal trichorrhexis nodosa | Pili canaliculi |
Bubble hair | |
Loose anagen hair |
Pseudomonilethrix
Pseudomonilethrix is a rare AD defect characterized by hair fragility. Localized or diffuse hypothicosis and fake knots (irregular hair shaft flattening) occur as the result of compulsive and frequent combing of the hair. Follicular hyperkeratosis is not observed. Individuals of different generations within the same family may be affected [10,11]. This condition may be associated with trichorrexis nodosa and bubble hair.
Genetics: Pseudomonilethrix is an AD defect. Specific genetic alterations have not been reported yet.
Clinical diagnosis: It is a familiar localized or diffuse hypotrichosis without follicular hyperkeratosis.
Optical microscopy: Rounded, normal appearing hairs with scarce and irregular oval or round nodules are present. Hair shaft narrowing is not observed (Figure 1.4).
Electron microscopy: What appear as nodules are actually flat segments of the hair shaft (Figure 1.5).
Trichoscopy: There are irregular distributed oval or round nodules without hair shaft narrowing segments and alternating of normal and wider segments of the hair shaft. No follicular hyperkeratosis is observed.
Acquired or Iatrogenic Pseudomonilethrix (Pseudopseudomonilethrix)
This defect is similar to pseudomonilethrix and arises from improper hair handling. It occurs when excessive pressure is applied to hair shafts during collection of samples from patients with monilethrix, woolly hair, and other conditions [12,13] (Figure 1.6). The same artifact is seen when a hair shaft is pressed between two slides (Figure 1.7).
Pili Torti
This disease involves braided hair with periodic ...