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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Neurology

Symptoms & Warning Signs of Untreated Biotinidase Deficiency

At a Glance

Untreated biotinidase deficiency causes a severe cellular energy shortage that can lead to seizures, severe skin rashes, hair loss, and permanent vision or hearing damage. Consistent, daily biotin treatment is essential to prevent these complications.

Because of newborn screening, most children with biotinidase deficiency will never experience a single symptom [1][2]. However, understanding the warning signs is vital. It highlights why daily treatment is absolutely non-negotiable and helps identify children who develop symptoms if treatment is delayed or stopped [3][4].

Without treatment, the body’s inability to recycle biotin leads to a severe shortage of cellular energy [5]. This affects the most sensitive systems first: the brain, the skin, and the senses [6][7].

Neurological Warning Signs

The brain and spinal cord are highly dependent on the “biotin cycle.” When it fails, several neurological issues can emerge:

  • Seizures: Often the first sign in untreated infants, these can range from subtle movements to major seizure events [7][8].
  • Hypotonia: Often described as “floppy baby syndrome,” where an infant has poor muscle tone, struggles with head control, and experiences developmental delays [7][6].
  • Ataxia: As children grow, they may appear unusually clumsy or have significant trouble with balance and coordination [7][9].
  • Myelopathy: In older individuals whose diagnosis was missed or who stopped taking biotin, the spinal cord can become damaged, leading to progressive weakness in the legs [7][8].

Skin and Hair (Cutaneous) Changes

Deficiency often shows up externally as skin and hair issues:

  • Intractable Dermatitis: This is a severe skin rash (often looking like eczema or a persistent diaper rash) that does not respond to typical creams or ointments [10][11].
  • Alopecia: Hair loss can be patchy or total [10][9].
  • Hair Discoloration: In some cases, the hair may take on a yellow tint before it falls out [10].

Vision and Hearing Loss

Unlike some skin or muscle symptoms that reverse quickly with biotin, damage to the eyes and ears can become permanent if not caught very early [12][9].

  • Progressive Optic Neuropathy / Optic Atrophy: The optic nerve (the cable from the eye to the brain) begins to waste away. This causes vision to slowly dim or blur until it is lost entirely [13][9].
  • Sensorineural Hearing Loss: This often manifests as auditory neuropathy or auditory dyssynchrony, where the ear can “hear” sounds, but the brain cannot organize them into clear information [14][15].

The Mimicker of MS and NMOSD

In teenagers or adults who were never screened as babies and went untreated, the neurological damage from biotinidase deficiency can look remarkably like other autoimmune diseases [16][9].

Because it causes vision loss and spinal cord damage (myelopathy), undiagnosed late-onset cases are frequently misdiagnosed as Multiple Sclerosis (MS) or Neuromyelitis Optica Spectrum Disorder (NMOSD) [8][11]. Fortunately, for children identified by newborn screening and treated from birth, these severe neurological outcomes are entirely preventable [1].

Common questions in this guide

What happens if biotinidase deficiency goes untreated?
Without daily treatment, the body cannot recycle biotin, causing a severe cellular energy shortage. This leads to serious neurological issues, skin rashes, hair loss, and potentially permanent damage to vision and hearing.
What are the early warning signs of biotinidase deficiency in babies?
Early signs in infants often include seizures and poor muscle tone, sometimes called floppy baby syndrome. Babies may also develop severe skin rashes that resemble diaper rash but do not clear up with typical ointments.
How is a biotinidase deficiency rash different from regular diaper rash?
The skin rash associated with this condition often looks like severe eczema or a persistent diaper rash. However, unlike common rashes, this intractable dermatitis will not respond to or clear up with typical skin creams and ointments.
Can missing biotin doses cause permanent damage?
Yes, if biotin treatment is delayed or stopped, certain symptoms can become permanent. While skin and muscle issues often improve once treatment resumes, damage to the optic nerve and hearing pathways may not be reversible.
Why is untreated biotinidase deficiency sometimes misdiagnosed in adults?
In older individuals who were not screened at birth, untreated deficiency causes spinal cord damage and progressive vision loss. These late-onset neurological symptoms look remarkably similar to autoimmune diseases like Multiple Sclerosis.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.My child seems to have a new symptom—is this a known sign of biotinidase deficiency or should we look for another cause?
  2. 2.If we accidentally missed a few doses of biotin, how quickly would we expect to see warning signs?
  3. 3.Can you check my child's vision for 'optic atrophy' and their hearing for 'sensorineural hearing loss' to ensure we have a baseline?
  4. 4.How do we distinguish a common diaper rash or eczema from the 'intractable dermatitis' associated with this condition?
  5. 5.Is my child at risk for 'late-onset' symptoms if we are consistent with treatment?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (16)
  1. 1

    Successful outcomes of older adolescents and adults with profound biotinidase deficiency identified by newborn screening.

    Wolf B

    Genetics in medicine : official journal of the American College of Medical Genetics 2017; (19(4)):396-402 doi:10.1038/gim.2016.135.

    PMID: 27657684
  2. 2

    Frequency of biotinidase gene variants and incidence of biotinidase deficiency in the Newborn Screening Program in Minas Gerais, Brazil.

    Carvalho NO, Januário JN, Felix GLP, et al.

    Journal of medical screening 2020; (27(3)):115-120 doi:10.1177/0969141319892298.

    PMID: 31801038
  3. 3

    Severe Distal Motor Involvement in a Non-compliant Adult With Biotinidase Deficiency: The Necessity of Life-Long Biotin Therapy.

    Van Winckel G, Ballhausen D, Wolf B, et al.

    Frontiers in neurology 2020; (11()):516799 doi:10.3389/fneur.2020.516799.

    PMID: 33192963
  4. 4

    Biotinidase deficiency should be considered in individuals exhibiting myelopathy with or without and vision loss.

    Wolf B

    Molecular genetics and metabolism 2015; (116(3)):113-8.

    PMID: 26358973
  5. 5

    Mutations in BTD gene causing biotinidase deficiency: a regional report.

    Kasapkara ÇS, Akar M, Özbek MN, et al.

    Journal of pediatric endocrinology & metabolism : JPEM 2015; (28(3-4)):421-4.

    PMID: 25423671
  6. 6

    Two novel BTD mutations causing profound biotinidase deficiency in a Chinese patient.

    Geng J, Sun Y, Zhao Y, et al.

    Molecular genetics & genomic medicine 2021; (9(2)):e1591 doi:10.1002/mgg3.1591.

    PMID: 33452876
  7. 7

    Brain MRI findings in an infant with congenital biotinidase deficiency.

    Singh P, Gurnani R, Rawat A, Parihar A

    BMJ case reports 2021; (14(10)) doi:10.1136/bcr-2021-246167.

    PMID: 34625444
  8. 8

    Atypical presentation of biotinidase deficiency: masquerading neuromyelitis optica spectrum disorder.

    Ali F, Mukhtiar K, Raza M, Ibrahim S

    BMJ case reports 2024; (17(7)) doi:10.1136/bcr-2023-258703.

    PMID: 38991566
  9. 9

    Biotinidase deficiency in differential diagnosis of neuromyelitis optica spectrum disorder.

    Bilge N, Yevgi R

    Multiple sclerosis and related disorders 2020; (44()):102280 doi:10.1016/j.msard.2020.102280.

    PMID: 32559702
  10. 10

    Biotinidase deficiency characterized by skin and hair findings.

    Yang Y, Yang JY, Chen XJ

    Clinics in dermatology 2020; (38(4)):477-483 doi:10.1016/j.clindermatol.2020.03.004.

    PMID: 32972606
  11. 11

    Biotinidase Deficiency: Report of a Tunisian Case With Neuromyelitis Optica-Like Presentation and Review of the Literature.

    Zioudi A, Benrhouma H, Jamoussi M, et al.

    Case reports in neurological medicine 2025; (2025()):7003370 doi:10.1155/crnm/7003370.

    PMID: 40171223
  12. 12

    Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review.

    Cao AA, Brown MM, Lee MS, et al.

    Neuro-ophthalmology (Aeolus Press) 2025; (49(3)):224-231 doi:10.1080/01658107.2024.2424209.

    PMID: 40190376
  13. 13

    Reversal of Vision Loss in a 49-Year-Old Man With Progressive Optic Atrophy Due to Profound Biotinidase Deficiency.

    Kellom ER, Wolf B, Rice GM, Stepien KE

    Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society 2021; (41(1)):e27-e30 doi:10.1097/WNO.0000000000000933.

    PMID: 32235217
  14. 14

    Auditory Neuropathy/Dyssynchrony in Biotinidase Deficiency.

    Talebi H, Yaghini O

    Journal of audiology & otology 2016; (20(1)):53-4 doi:10.7874/jao.2016.20.1.53.

    PMID: 27144235
  15. 15

    Biotinidase deficiency: A treatable cause of opticospinal syndrome in young adults✰.

    Van Iseghem V, Sprengers M, De Zaeytijd J, et al.

    Multiple sclerosis and related disorders 2019; (32()):64-65 doi:10.1016/j.msard.2019.04.025.

    PMID: 31035122
  16. 16

    Biotinidase deficiency should be considered in individuals thought to have multiple sclerosis and related disorders.

    Wolf B

    Multiple sclerosis and related disorders 2019; (28()):26-30 doi:10.1016/j.msard.2018.11.030.

    PMID: 30551056

This page explains the symptoms of untreated biotinidase deficiency for educational purposes only. Always consult your pediatrician or metabolic specialist about any new symptoms, missed doses, or treatment concerns for your child.

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