Hair Shaft Disorders Research Articles

Síndrome de Netherton

Netherton syndrome is a rare disease inherited as an autosomal recessive trait due to mutations in the SPINK5 gene. It is characterized by the triad of ichthyosiform dermatosis, alterations of the hair shaft and immunological disorders. We present the case of a 12-year-old girl with the triad of ichthyosis linearis circumflexa, trichorrhexis invaginata and atopic dermatitis, characteristic of Netherton syndrome.

A Gene for Pili Annulati Maps to the Telomeric Region of Chromosome 12q

Pili annulati (PA) is a rare hair shaft disorder characterized by discrete banding of hairs. We studied two families with PA in which the disorder segregated in an autosomal dominant fashion. All family members were clinically examined and hair samples were examined under the light microscope. In family G, of 19 individuals examined, ten were affected, over three generations. In family B, there were three affected individuals of seven examined over three generations. A genome-wide scan of family G revealed a maximum logarithm of odds (LOD) of linkage score of 3.89 at marker D12S1723 at the telomeric region of chromosome 12q. From one critical recombinant in family G, the locus was narrowed down to a 9.2 cM region between D12S367 and the end of chromosome 12q. In family B linkage at the telomeric region of chromosome 12q also revealed a maximum LOD score of 0.89 at marker D12S1723. A combined LOD score, assuming no locus heterogeneity between the families was 4.78. Frizzled 10, which is located within the region, was sequenced but we were unable to detect a mutation causing PA. This study, for the first time, identifies a genetic locus for PA.

De novo mutations in monilethrix

Mutations in the hair keratins hHb1 and hHb6 have been recently reported to cause monilethrix, an autosomal dominant hair shaft disorder, characterized by variable degrees of hair fragility and follicular hyperkeratosis. We found 10 families with monilethrix in whicn the parents were not clinically affected, and sequenced the hair keratin hHb1, hHb2 and hHb6 genes in seven patients. In five patients no mutations were found, while in two patients we identified de novo germline missense mutations at the helix termination motif: E402K (hHb6) and E413K (hHb1).

"Curly" wood and tiger tails: an explanation for light and dark banding with polarization in trichothiodystrophy.

The mechanism causing the tiger tail phenomenon in trichothiodystrophy (alternating light and dark banding of hair shafts when examined with polarized light) has yet to be explained with certainty. However, we propose a simple and easily tested hypothesis to explain its striking aspect. Although the hair shafts we obtained from patients with trichothiodystrophy were fairly straight, the cortical hair fibers were not. We noticed that these fibers undulate up and down (or back and forth), a feature that is easily observed because of melanin granules embedded in each fiber. The undulations correspond exactly to the banding seen with polarization. Therefore, the tiger tail phenomenon seen in trichothiodystrophy and other hair shaft disorders is caused by a regular undulation of hair fibers within the shafts. Normal hair shafts do not exhibit the phenomenon because the hair fibers are straight and parallel to the long axis of the hair. It is the regular undulation of fibers that changes the optical properties of the hair shafts and causes a predictable banding when the shafts are examined by polarized light.

Hair shaft abnormalities

Hair shaft disorders may lead to brittleness and uncombable hair. In general the hair feels dry and lusterless. Hair shaft abnormalities may occur as localized or generalized disorders. Genetic predisposition or exogenous factors are able to produce and maintain hair shaft abnormalities. In addition to an extensive history and physical examination the most important diagnostic examination to analyze a hair shaft problem is light microscopy. Therapy of hair shaft disorders should focus to the cause. In addition, minimizing traumatic influences to hair shafts, such as dry hair with an electric dryer, permanent waves and dyes is important. A short hair style is more suitable for such patients with hair shaft disorders.

Trichothiodystrophy: Update on the sulfur-deficient brittle hair syndromes

Trichothiodystrophy (TTD) refers to a heterogeneous group of autosomal recessive disorders that share the distinctive features of short, brittle hair and an abnormally low sulfur content. Within the spectrum of the TTD syndromes are numerous interrelated neuroectodermal disorders. The TTD syndromes show defective synthesis of high-sulfur matrix proteins. Abnormalities in excision repair of ultraviolet (UV)-damaged DNA are recognized in about half of the patients. Three distinct autosomal recessive syndromes are associated with nucleotide excision repair (NER) defects: the photosensitive form of TTD, xeroderma pigmentosum, and Cockayne syndrome. The unifying feature of these conditions is exaggerated sensitivity to sunlight and UV radiation. In contrast to patients with xeroderma pigmentosum, no increase of skin cancers in patients with TTD has been observed. Genetically, 3 complementation groups have been characterized among photosensitive patients with TTD. Most patients exhibit mutations on the two alleles of the XPD gene. Rarely, mutated XPB gene or an unidentified TTD-A gene may result in TTD. In UV-sensitive TTD, the TFIIH transcription factor containing XPB and XPD helicase activities necessary for both transcription initiation and DNA repair is damaged. Beyond deficiency in the NER pathway, it is hypothesized that basal transcription may be altered leading to decreased transcription of specific genes. Depressed RNA synthesis may account for some clinical features, such as growth retardation, neurologic abnormalities, and brittle hair and nails. Therefore the attenuated expression of some proteins in differentiated cells is most likely explained by a mechanism distinct from DNA repair deficiency. The first transgenic mouse models for NER deficiencies have been generated. The TTD mouse as well as related cell models will provide important tools to understand the complex relationships between defects in DNA repair, low-sulfur hair shaft disorders, and the genotype-phenotype correlates for this constellation of inherited disorders, including the lack of predisposition to cancer in patients with TTD. (J Am Acad Dermatol 2001;44:891-920.) Learning objective: At the completion of this learning activity, participants will have a current understanding of the expanded and further defined clinical spectrum of the TTD syndromes. Participants will have gained new insight into the genetic and molecular characteristics and causes for the low-sulfur hair disorders.

Scanning Electron Microscopy Study of Hair Shaft Disorders in Psoriasis

Studies on scalp hair from psoriatic lesions have revealed marked irregularities in the cuticular pattern. The aim of this study was to investigate the incidence of hair shaft disorders in psoriatic patients and to evaluate the possibility of a correlation with scalp involvement. We examined hair from 39 psoriatic patients using scanning electron microscopy and compared it with hair from a control group of 12 healthy people. We confined our observations of the hair fibres to the areas nearest the root. Our data confirm previous observations indicating that dystrophic changes in hair cuticle cells occur more often in hairs from both unaffected and affected skin of psoriatic patients compared with normal subjects. No differences were observed between hair shafts taken from affected and unaffected psoriatic areas; cuticular breakage and an abraded cuticular surface were present only in the hair of psoriatic patients.

AN UPDATE OF HAIR SHAFT DISORDERS

Most of the congenital and hereditary hair shaft abnormalities were well described many years ago in relation to the clinical and microscopic characteristics. Because of this, and in view of the fact that many of these have obvious pedigrees, there is feasibility of targeted topical selective gene therapy being developed for hair follicle fa~lts.9~ The unprecedented developments in molecular genetics in the past decade have led some sophists to predict a future like Aldous Huxley's Brave New World. Impressive progress has been made in our knowledge of genes that control normal development and differential, and the search is on to define these in hair diseases. At this stage of our knowledge, it is therefore important to lay down the up-to-date clinical and laboratory diagnostic criteria. Only those well-known conditions in which this information is accurately known are considered here. If more detail of other entities is required, more comprehensive texts should be Price118 classifies anomalies of the shaft into those that are associated with increased fragility, and those that are not. This distinction is useful because only the former present clinically as patchy or diffuse alopecia. The weathering process should be understood as a background to any overall assessment of hair shaft disorders. It is present in all people and lends features to both normal hair and hair with intrinsic weakness, such as that seen in trichothiodystrophy.

Heritable Disorders of Hair

Changes in the quality and quantity of hair occur in a large number of hereditary syndromes. Because of their rarity and our lack of knowledge about their pathophysiology, no entirely satisfactory classification of these hair disorders exists. This review arbitrarily groups the heritable disorders of the hair into five classes: primary hair shaft disorders, alopecia without associated defects, ectodermal dysplasias, changes in hair color, and ectopic hair.

Clinical pathologic conference

Trichorrhexis nodosa is a hair shaft disorder presented with whitish nodes all over the hair (diffuse form) or localized to an area (localized form) and could be either congenital or acquired. We are reporting a case of acquired localized form of trichorrhexis nodosa due to trauma (physical–chemical).