Initially described 50 years ago, Bjornstad syndrome (BS) is a rare genetic disorder that arises due to mutations in BCS1L proteins that play an essential role in mitochondrial function [1] [2] [3] [4]. The location of genes that code for these proteins was subsequently identified on chromosome 2 and an autosomal recessive pattern of inheritance was established [1] [2] [3]. Very few cases of BS have been described in the literature. The clinical presentation is centered around two components - pili torti and hearing loss [3] [5] [6]. Pili torti (denoting the twisting of hair around their axis) is a term used to illustrate the appearance of short and brittle hair (without any pigment) that occurs as a result of the previously mentioned mutations, consequently leading to hair loss in the first few years of life [1] [5] [6]. For some reason, the hair on the head is principally affected, whereas the other parts of the body (including the face) are spared. Conversely, hearing loss is congenital in nature and develops by three years in the majority of cases [1] [5]. The severity of hearing impairment may be mild, moderate, or severe enough to lead to deafness [1] [3]. Isolated studies have reported mental retardation and hypogonadism as additional signs of BS [5].

• Male Hypogonadism

  Underdevelopment of the ovaries of affected females or the testes of affected males (hypogonadism) has occurred in association with Björnstad syndrome. [rarediseases.org]

• Vomiting

  A 9-month-old boy presented with the complaints of loose motion, vomiting and difficulty in breathing. His scalp hairs were thin, brittle, and sparse and were of differing lengths with twisted appearance. [ncbi.nlm.nih.gov]

  Abstract A 9-month-old boy presented with the complaints of loose motion, vomiting and difficulty in breathing. His scalp hairs were thin, brittle, and sparse and were of differing lengths with twisted appearance. [link.springer.com]

  QTc 64 While we still recommend the simple preventive measures of QT drug avoidance, electrolyte/hydration replenishment particularly in the setting of vomiting and diarrheal illnesses where hypokaliemia could occur, and use of antipyretics to lower fever [academic.oup.com]

• Arthritis

  5221 Email: [email protected] Internet: Better Hearing Institute 1444 I Street NW Suite 700 Washington, D.C. 20005 United States Tel: (202)449-1100 Fax: (703)684-6048 Tel: (800)327-9355 Email: [email protected] Internet: NIH/NationaI Institute of Arthritis [healthmedicinet.com]

  5221 Email: [email protected] Internet: Better Hearing Institute 1444 I Street NW Suite 700 Washington, D.C. 20005 United States Tel: (202)449-1100 Fax: (703)684-6048 Tel: (800)327-9355 Email: [email protected] Internet: NIH/National Institute of Arthritis [informationtherapy.in]

  Gaithersburg, MD 20898-8126 Phone: (301) 251-4925 Toll-free: (888) 205-2311 Website: Hearing Loss Association of America 7910 Woodmont Avenue Suite 1200 Bethesda, MD 20814 Phone: (301) 657-2248 Email: [email protected] Website: NIH/National Institute of Arthritis [rarediseases.org]

• Alopecia

  Set Front Back Clinical Inheritance Autosomal recessive; 2q34 q36 gene locus Prenatal None listed Incidence Very rare approximateIy 25 cases reported; M F Age at Presentation By 2 years old Pathogenesis Unknown Clinical Hair Pili torti with/without alopecia [cram.com]

  Abnormalities of hair (alopecia, or coarse, dry, lusterless, fragile hair) are present and mainly of cosmetic concern. Microscopic examination of the hair shaft shows flattening at irregular intervals and a 180-degree twisting around its axis. [accessanesthesiology.mhmedical.com]

  Symptoms may include: dry, fragile, or course hair, or patches of hair loss (alopecia). Both hearing problems, which can range from mild to severe, and abnormal hair present before the age of two. [globalgenes.org]

• Anhidrosis

  Hypogonadism Decreased activity of gonads 0000135 Intellectual disability Mental deficiency Mental retardation Mental retardation, nonspecific Mental-retardation [ more ] 0001249 Percent of people who have these symptoms is not available through HPO Anhidrosis [rarediseases.info.nih.gov]

  In addition, the eyes of the affected males and females were of light color and all the patients had anhidrosis. Teeth, nails, palms and soles were normal in all the affected individuals. [doi.org]

  […] failure 8 613957 N S D 1 5q35.2-q35.3 Beckwith-Wiedemann syndrome 130650 Leukemia, acute myeloid 601626 Sotos syndrome 1 117550 N S U N 2 5p15.31 Mental retardation, autosomal recessive 5 611091 N TRK1 1q23.1 Insensitivity to pain, congenital, with anhidrosis [institutobernabeu.com]

• Hearing Impairment

  Björn·stad syn·drome ( byōrn'stahd ), [MIM*262000] pili torti associated with sensorineural hearing loss, the severity of distortion and brittleness of the hair correlated with the degree of hearing impairment; autosomal dominant inheritance. [medical-dictionary.thefreedictionary.com]

  The severity of hearing impairment may be mild, moderate, or severe enough to lead to deafness. Isolated studies have reported mental retardation and hypogonadism as additional signs of BS. [symptoma.com]

  impairment; autosomal dominant inheritance. [checkorphan.org]

  In addition the patients had a moderate-to-severe degree of hearing impairment. Genotyping with high-density single-nucleotide polymorphism arrays showed homozygosity in two intervals on chromosome 2. [uniprot.org]

• Normal Hearing

  Hearing loss, but not pili torti, occurs in complex III deficiency 12 ; neither is a typical feature of the GRACILE syndrome, perhaps because recognition of the syndrome is hindered by complex systemic manifestations and early death. [content.nejm.org]

• Neurologic Manifestation

  In addition to the Björnstad syndrome, BCS1L mutations cause complex III deficiency and the GRACILE syndrome, which in neonates are lethal conditions that have multisystem and neurologic manifestations typifying severe mitochondrial disorders. [ncbi.nlm.nih.gov]

  manifestations such as hypotonia or ataxia (Rahman and Thorburn. 2015. [preventiongenetics.com]

Given the rare occurrence of Bjornstad syndrome in clinical practice (approximately 20 cases have been described by the end of the 20th century) [2], the diagnosis may be difficult to attain. For this reason, the physician must obtain a detailed patient history and perform a meticulous physical examination that will provide the opportunity to identify the hallmarks of BS. The onset of deafness and hair loss must be assessed with the parents of the affected child, as most cases are described in infancy or early childhood. In addition, a complete family history that covers the presence of similar findings in siblings or parents might be of great benefit for raising clinical suspicion toward a familial disorder. Auditory testing should be conducted in order to determine the extent of hearing loss, whereas microscopic examination of the hair will reveal typical twists of the hair shaft that must point to BS [4] [7]. Transmission electron microscopy (TEM) has been used (where possible) as a method to confirm pili torti [4] [6]. To confirm the diagnosis, however, genetic testing to detect BCS1L mutations is a mandatory procedure.

1. Hinson JT, Fantin VR, Schönberger J, et al. Missense mutations in the BCS1L gene as a cause of the Björnstad syndrome. N Engl J Med. 2007;356(8):809-819.
2. Lubianca Neto JF, Lu L, Eavey RD, et al. The Bjornstad syndrome (sensorineural hearing loss and pili torti) disease gene maps to chromosome 2q34-36. Am J Hum Genet 1998;62:1107-1112.
3. Siddiqi S, Siddiq S, Mansoor A, et al. Novel mutation in AAA domain of BCS1L causing Bjornstad syndrome. J Hum Genet. 2013;58(12):819-821.
4. Zhang J, Duo L, Lin Z, et al. Exome sequencing reveals novel BCS1L mutations in siblings with hearing loss and hypotrichosis. Gene. 2015;566(1):84-88.
5. Selvaag E. Pili torti and sensorineural hearing loss: a follow-up of Bjornstad's original patients and a review of the literature. Eur J Dermatol. 2000;10:91-97.
6. Marubashi Y, Yanagishita T, Muto J, et al. Morphological analyses in fragility of pili torti with Björnstad syndrome. J Dermatol. 2017;44(4):455-458.
7. Scott MJ Jr, Bronson DM, Esterly NB. Björnstad syndrome and pili torti. Pediatr Dermatol. 1983;1(1):45-50.