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PubMed1999

Two different mutations in the same codon of a type II hair keratin (hHb6) in patients with monilethrix.

Monilethrix is an autosomal dominant hair disorder characterized by a beaded appearance of the hair due to periodic thinning of the shaft. The phenotype shows variable penetrance and results in hair fragility and patchy dystrophic alopecia. Mutations of the helix-encoding region in two hair-specific keratins (hHb1 and hHb6) have been identified. We have now investigated two unrelated monilethrix patients and identified two different novel heterozygous point mutations of the same codon in exon 7 of the hHb6 gene. Dystrophic hair samples obtained from both patients showed the typical beaded appearance by scanning electron microscopy. Both mutations affected the first base of codon 402 (glutamic acid). In patient A, a G to C transition occurred causing a glutamine substitution (GAG to CAG: E402Q) whereas in patient B, the transition was G to A yielding a lysine substitution (GAG to AAG: E402K). The sequence of the 1A helical regions of hHb1 and hHb6 as well as the 2B helical region of hHb1, were normal. Unaffected relatives did not have the hHb6 mutation and this codon was found to be highly conserved showing no alteration in the normal population (100 alleles examined). Both mutations disrupted a Taq I restriction site and restriction fragment length polymorphism analysis showed that a diagnostic 361 bp fragment could confirm the mutation. Thus, two new point mutations of the hair-specific keratin gene hHb6 have been identified in this genetic disease.

Alopecia↗
PubMed1995

A gene for monilethrix is closely linked to the type II keratin gene cluster at 12q13.

Monilethrix is an uncommon hereditary disorder of hair and nail which produces hair fragility and a variable alopecia. Many of the dystrophic hairs have a unique beaded morphology. Ultrastructural changes suggest a defect in the microfilament structure of the cortex of the hair shaft,and hence the cysteine-rich trichocyte keratins are candidate genes. Here, in two families with autosomal dominant monilethrix, we have excluded linkage to the type I keratin gene cluster on chromosome 17q, but show that the disorder is closely linked to the type II keratin cluster on 12q, where genes for basic trichocyte keratins are found. The combined maximum lod score for D12S96 was 12.27 at theta=0.0. This is the first mapping of a primary human hair disorder and the first evidence implicating a defect of the word 'hard' keratins of hair and nail disease.

Chromosomes, Human, Pair 12↗
PubMed1990

Pathogenesis of monilethrix: computer stereography and electron microscopy.

The plucked hairs and biopsied hair follicles of the scalp were obtained from a female patient with monilethrix. By scanning electron microscopy, the plucked hairs showed a typical moniliform feature composed of alternated nodes and internodes. By computer stereography, reconstructed three-dimensional models of in vivo hair structures showed that the diameter of hair shaft was partially reduced in the keratogenous zone and that the reduction was severe in the hair cortex and cuticle layers but mild in the inner root sheath. By transmission electron microscopy, a significant degeneration of hair matrix cells was found, and a zig-zag disarray of cortical tonofibrils and invaginations of the hair cuticle cells into the cortex were noticed in the suprabulbar portion. In some hairs, the hair bulbs showed no degeneration, but a degeneration of cortical cells and invaginations of hair cuticle were seen in some portions in the developing zone of the cortex. This suggests that not every hair matrix is damaged in a synchronized fashion, but individual hairs are affected independently. Furthermore, in all the hair and hair follicles examined, cytoplasmic vacuolations were always seen in the various layers, and abnormal formation of tonofibrils was often observed in the cortex. In monilethrix, a cell abnormality may inherently be present in the hair tissue and, when such abnormality occurs severely, the cortical cells are particularly affected in the hair matrix. This seems to result in a decrease in number of cortical cells and thinning of the hair shaft.

Child, Preschool↗
PubMed2003

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).

Amino Acid Motifs↗
PubMed1981

Monilethrix: an electron microscopic and electron histochemical study.

We have carried our electron microscopic and electron histochemical investigations on affected hair follicles and hair shafts to elucidate further the structural abnormality in monilethrix. The structural abnormalities manifest in the cortex and cuticle of the hair shaft could be traced to the locality of the 'zone of keratinization' of the follicle. Abnormal orientation of the cortical cell proteins, folding of the cuticle cell membrane and varying amounts of endocuticular material were all observed in the region prior to full keratinization. We observed structural abnormalities within all the component layers of the inner root sheath adjacent to the faults within the hair shaft, indicating a possible asynchrony within the monilethrix follicle.

Hair↗
PubMed1993

Monilethrix: a clinicopathological illustration of a cortical defect.

We describe two sisters aged 2 and 7 years, with monilethrix. The older sister was clinically less severely affected but, microscopically, the features of weathering and alternating nodes and internodes were more obvious. The younger girl had more severe alopecia, with shorter hair, but the microscopic features were less marked. Scanning-electron microscopy demonstrated only slight cuticular weathering in both cases, and evidence of breakage in the cuticle at points of no obvious cuticular pathology. Transmission-electron microscopy showed normal cuticle cells in cross-section, but an abnormal cortex. The abnormalities included areas of homogeneous non-fibrillar material, and a deviated axis of some microfibrils. We consider that these findings support the possibility that a cortical defect contributes significantly to the fragility of hair in monilethrix. This might explain why hair with marked beading can be stronger than hair from an affected sibling with less apparent abnormality.

Child↗
PubMed1992

Variations in the beading configuration in monilethrix.

Using information from a light microscope integrated with a computer, we quantified the variation in node and internode dimensions in monilethrix. We combined this with rate of growth measurements in individual hairs to make the following conclusions. There is considerable variation of node and internode configuration within single hairs. Hairs from the same scalp, sampled at the same time show no mutual coordination of node-internode formation, even when different growth rates are taken into account. There is no apparent correlation between the day-night cycle and the node-internode rhythm. The follicular expression of monilethrix appears largely independent of unifying systemic influences.

Adult↗
PubMed2003

Recurrent E413K mutation of hHb6 in a Japanese family with monilethrix.

Monilethrix is an autosomal dominant hair disorder characterized by a beaded appearance of the hair due to periodic thinning of the shaft. This disorder has been reported to be caused by mutations in the helix termination motif of two type II cortex keratins, hHb1 and hHb6. Here we describe a Japanese monilethrix family that has the most frequent mutation, the E413K mutation in hHb6, so far found in 26 families. Genotype/phenotype correlation was not obvious in our case or in the previously reported cases.

Child, Preschool↗
PubMed2005

Monilethrix: improvement with acitretin.

Monilethrix is a rare hereditary disorder that affects the hair and is characterized by shaft anomaly. There is no known treatment that successfully cures the condition. In this report we present a case of monilethrix in a 7-year-old girl treated with oral acitretin. A very good clinical and cosmetic result was obtained while treatment was continued. However, clinical symptoms recurred after discontinuation of acitretin therapy.

Acitretin↗
PubMed1999

[Monilethrix--rare syndrome of structural hair abnormalities].

Monilethrix is a rare structural disorder of hair. Characteristic abnormalities in the form of alternating thinning and fusiform thickening are observed in most of hair shafts that we call beaded hair. Macroscopic estimation shows lustreless, dry, rough, fragile hair. Trichological examination usually reveals a considerable percentage of anagenic hair. According to our own experiences and literature data systemic therapy (vitamins) and topical treatment (desquamative ointments) are not effective sufficiently. Spontaneous regression of symptoms often appears with time. Five cases of familial occurrence of monilethrix have been presented.

Child↗
PubMed1992

Review and new case reports on scanning electron microscopy of pili annulati, Monilethrix and Trichothiodystrophy.

Pili annulati, Monilethrix and Trichothiodystrophy are uncommon conditions in which the hair shaft has a distinct appearance as seen by optical microscopy and scanning electron microscopy (SEM). We report several new cases and review the characteristic ultrastructural abnormalities investigated by SEM. Pili annulati: abnormal areas which show a longitudinal, "curtain-like" folding of the cuticular cells, alternating with normal areas. The latter present regularly non-systematized, superficial depressions. Hair specimens of the patient's mother show the same surface irregularities. Monilethrix: most hair shafts show variations in thickness giving a typical nodal appearance. In the isthmus area we noticed longitudinal ridging and cuticular scales that are extended lengthwise in a fish-scale-like pattern. In the nodus area a smooth surface due to a complete loss of cuticular cells, was observed. Trichothiodystrophy: the hair morphology observed by SEM is characterized by severe cuticular and secondary cortical degeneration along the entire length of the flattened hair shaft, with longitudinal ridging, cuticle loss, trichlorrhexis nodosa formation and trichoschisis. SEM observations show morphological abnormalities which are characteristic for each pathological condition described. This method may provide data that add some clarity in the surface changes of the different hair shaft anomalies.

Adult↗
PubMed1979

[Studies on monilethrix].

Monilethrix is a disorder of the hair manifested by fragile, beaded hair and baldness. The four children described below showed no regulary rhythm of node and internode formation. Light microscopy supported the hypothesis that periodic inhibition of keratin synthesis explains the production of the constriction. Scanning electron microscopy shows longitudinal ridging of the internodes in monilethrix and distinctive surface irregularity. Chromatography of urine for argininosuccinic acid do not support the theory that this hair abnormality is a metabolic defect.

Argininosuccinic Acid↗
PubMed1984

[Monilethrix: exclusive involvement of body hair].

In a family suffering from monilethrix, at first sight only one generation seemed to be affected, suggesting a recessive mode of inheritance. A thorough examination of the scalp and body hair of all family members, however, revealed three other affected persons in two more generations proving autosomal dominant transmission. We consider this observation an additional argument against the existence of a recessive type of monilethrix which has been postulated in the past.

Adult↗
PubMed1982

The genetic analysis of monilethrix in a large inbred kindred.

The gene for monilethrix was segregating in a large inbred kindred. Pedigree analysis reaffirms an autosomal dominant mode of inheritance. Expressivity appears equally variable within and between sibships while penetrance, in contrast to previous studies, seems to be complete.

Consanguinity↗
PubMed2006

Mutations in the desmoglein 4 gene underlie localized autosomal recessive hypotrichosis with monilethrix hairs and congenital scalp erosions.

Localized autosomal recessive hypotrichosis (LAH) is a recently defined disorder characterized by fragile, short, sparse hairs on the scalp, trunk, and extremities. Mutations in desmoglein 4 (DSG4), a novel member of the desmosomal cadherin family that is expressed in the hair follicle as well as the suprabasal epidermis, have been found to underlie LAH. Thus far, the allelic series includes a recurrent intragenic deletion identified in affected Pakastani kindreds and a missense mutation detected in an Iraqi family. We report three siblings of Iraqi and Iranian origin with LAH that presented with congenital scalp erosions and monilethrix-like hairs, features that have not been previously described in this disorder. Follicular hyperkeratotic papules and marked pruritus were also prominent clinical findings. Novel compound heterozygous DSG4 mutations, including a splice-site mutation and a missense mutation that disrupts a conserved calcium-binding site in the extracellular (EC)2-EC3 interface, were found to underlie the disease in this family. These observations broaden the phenotypic and genotypic spectrum of LAH, further illustrating the consequences of DSG4 dysfunction on epidermal and hair shaft integrity.

Amino Acid Sequence↗
PubMed2006

More than one gene involved in monilethrix: intracellular but also extracellular players.

Monilethrix, an autosomal dominant human hair disorder, is caused by mutations in three type II hair cortex keratins. Rare cases of the disease with non-vertical transmission have now been found to overlap with localized autosomal recessive hypotrichosis. The underlying gene, desmoglein 4 (DSG4), belongs to the desmosomal cadherin superfamily and is also expressed in the cortex of the hair follicle.

Animals↗
PubMed2001

Keratosis pilaris and hereditary koilonychia without monilethrix.

Keratosis pilaris is found commonly in isolation as well as associated with other conditions. We describe a family with keratosis pilaris and hereditary koilonychia, with an autosomal dominant pattern of inheritance. These two findings have only been previously found in the context of monilethrix. The coexistence of the two disorders suggests a close association of their genetic pathogenesis.

Adult↗