Monilethrix:a Pedigree Report And Review Of The Literatures

Background and objective: Monilethrix is a rare autosomal dominant genetic disease that causes hairs to a characteristic beaded appearance and leads to localized or generalized hair loss with or without hair follicle lesions,and is also reported in recessive cases.Mutations in the human hair keratin(hHb)with chromosome 12q13 lead to autosomal dominant monilethrix whereas mutations in the desmoglein 4 gene cause an autosomal recessive form.The disease not only affect the physical and mental health due to abnormal appearance of hair and hair loss,but also accompanied by koilonychia,keratosis pilaris,syndactylia,cataract,dental abnormalities and scarring alopecia,so affect the patients’ quality of life seriously.In this study,we observe the clinical phenotype,the structure of the hair shaft and the treatment of the patients in the sichuan province of a series of two cases,and then detect the pathogenic gene and provide a review of the literature.The purpose of this study is to understand the clinical characteristics,the ultrastructure of hair shaft and the genetic characteristics of the disease better,and to observe the therapeutic effect of oral acitretin.Methods: Two cases of Monilethrix were reported,who were admitted to the dermatology of Children’s Hospital of Chongqing Medical University.We collect the clinical data(medical history,physical examination and family survey),observe the microstructure and ultrastructure of hair shaft(dermatoscope,light microscope and scanning electron microscope),detect the pathogenic gene and follow up the curative effect of oral acitretin.Results: 1.The proband was a 3-year-old male,who was admitted to the dermatology clinic of our hospital in February 2017 because of the fragile hair of occiput for 3 years.The occipital hair became brittle,detached and sparse in the second and third months of life,at the same time,the occipital scalp showed keratotic follicular papules and erythema,which has been exacerbated in the winter and summer remission.No obvious abnormalities were observed in the physical examination of each system.There were many beam-like hairs and keratotic follicular papules can be seen under the dermatoscope.Under the light microscope,the hair shaft showed a characteristic anomaly named beaded hair or moniliform hair with periodic changes in hair diameter,leading to form nodes and internodes.The hair diameter of the swollen part is normal,while the hair of the constricted part is often unmedullated and easily broken.No fungal hyphae and spores were found in the hair or out of the hair.Scanning electron microscopy(SEM)showed that the abscission of the cuticula pilion the surface of hair.The expanded part can be seen in the normal imbricate arrangement of the cuticula pili,while the cuticula pili of the constricted part is arranged in disorder.The longitudinal ridge and groove can be seen in the joint of the swollen segment and the constricted section.A heterozygous mutation(E402K)was found in extron7 of hHb6.There was an improvement in the hair keratotic follicular papule after 1month of oral acitretin,but no significant improvement was found in the hair shaft structure.2.The mother of the proband,female,30 years old.The symptoms were similar to those of the proband.There was a significant period of remission in pregnancy,but the hair was restored after delivery.No obvious abnormalities were observed in the physical examination of each system.A heterozygous mutation(E402K)was found in extron7 of hHb6.Conclusion: 1.Patients of monilethrix are usually diagnosed after a few months of birth.The symptoms are often aggravate in winter.Some patients can improve their symptoms with age,puberty and pregnancy.2.The expanded part can be seen in the normal imbricate arrangement of the cuticula pili,while the cuticula pili of the constricted part is arranged in disorder under the SEM.It may be suggested that the constricted part is the main site of the lesion.Hair structure examination can be used as a simple and sufficiently screening method for clinical diagnosis.3.The mutation of the extron7 of h Hb6 gene plays an important role in thepathogenic mechanism of this pedigree with monilethrix.The E402 K mutation of the hHb6 gene may be a hot spot of mutation in Chinese.Further information may be used in prenatal gene diagnosis.4.At present,there is no specific treatment for monilethrix.Oral acitretin can improve the keratosis papules of hair follicle,but it has no obvious effect on hair shaft structure.