title: Congenital atrichia and hypotrichosis.
abstract: BACKGROUND
  Alopecia present from birth includes a broad differential diagnosis and often represents a diagnostic and therapeutic challenge for the involved physician.
  
  
  METHODS
  An initial correct diagnosis and classification is essential because structural hair defects may be the expression of a genetic disorder affecting hair growth, part of a congenital syndrome with accompanying hair malformations, or a marker for an underlying metabolic disorder and may impact the mental and physical development of a child. Pathological hair loss rarely occurs in the first year of life; however, it may be a leading symptom of many congenital diseases.
  
  
  RESULTS
  In recent years, the clinical and microscopic features of hereditary hair shaft disorders have been characterized and classified. Furthermore, significant progress has been made in our knowledge of genes that control the normal development and differentiation of hair follicles, and thus the research is to define and classify the hair disorders within a genetic basis.
  
  
  CONCLUSIONS
  In this article we discuss several types of genotrichosis and provide a practical classification based on their clinical features.
authors.affiliation: Department of Dermatology, Hospital Clínic, University of Barcelona, Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Bennàssar
authors.forename: Juan
authors.initials: J
authors.lastname: Ferrando
authors.forename: Ramon
authors.initials: R
authors.lastname: Grimalt
mesh_terms: D000505:Alopecia / Q000151:congenital* / Q000235:genetics; D000783:Aneurysm / Q000175:diagnosis; D002280:Basal Cell Carcinoma / Q000175:diagnosis; D002648:Child; D002971:Cleft Lip / Q000175:diagnosis; D002972:Cleft Palate / Q000175:diagnosis; D003638:Deafness / Q000175:diagnosis; D004476:Ectodermal Dysplasia / Q000175:diagnosis; D004485:Eczema; D019066:Facies; D005385:Fingers / Q000002:abnormalities; D006130:Growth Disorders; D006201:Hair Diseases / Q000175:diagnosis; D006210:Hallermann's Syndrome / Q000175:diagnosis; D018219:Histiocytoma, Benign Fibrous / Q000175:diagnosis; D006801:Humans; D007039:Hypotrichosis / Q000175:diagnosis / Q000209:etiology / Q000235:genetics*; D007057:Ichthyosis / Q000175:diagnosis; D008607:Intellectual Disability; D007634:Keratitis / Q000175:diagnosis; D015826:Langer-Giedion Syndrome / Q000175:diagnosis; D008831:Microcephaly; D009666:Nose / Q000002:abnormalities; D012873:Skin Diseases, Genetic / Q000150:complications / Q000175:diagnosis*; D012878:Skin Neoplasms / Q000175:diagnosis