Introduction
Biotin serves as a cofactor for four human carboxylases pyruvate carboxylase, propionyl-coenzyme A (CoA) carboxylase, beta-methylcrotonyl-CoA carboxylase, and acetyl-CoA carboxylase which are involved in fatty acid synthesis, amino acid catabolism, and gluconeogenesis.[1] BD is caused by the low activity of the biotinidase enzyme which recycles endogenous biotin.[2]
Case report
A 4-year-old female child born out of third-degree consanguineous marriage presented with cutaneous lesions around the eyes and mouth along with sparseness of scalp hair for the last 2 years. She was born at full term after an uneventful pregnancy by normal vaginal delivery. The child had a birth weight of 3.2 kg, a length of 54 cm and was properly breastfed. There was a global developmental delay, gait disturbance along with hearing impairment. There was a history of hospitalization for breathlessness 3 months back. There was no history of diarrhoea, seizure, or ophthalmological complaints. Family history was unremarkable.
On general examination, the patient was afebrile, had an ataxic gait, and was tachypneic with a respiratory rate of 54/minute. The anthropometric measurements were within normal limits for age.
Cutaneous examination revealed periocular and perioral desquamating lesions with secondary impetiginization [Figure 1]. Scalp examination revealed diffuse thinning of hair along with widening of central parting [Figure 2] and alopecia involving the occiput [Figure 3], however, the trichogram was normal. Nails and mucosae were uninvolved.
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Figure 1: Periocular and perioral desquamating lesions with secondary impetiginization
Figure 2: Diffuse thinning of scalp hair along with widening of central parting
Figure 3: Alopecia involving the occiput
A neurological assessment showed hypotonia along with grade 2 hyper-reflexia and a positive bilateral Babinski.
Hemogram, liver and renal function tests, random blood sugar, thyroid function test, and serum electrolytes were within normal limits. Chest radiograph, electroencephalogram, and computed tomography scan of the head revealed no abnormality. Complete ophthalmological examination along with fundoscopy was within normal limits. Arterial blood gas analysis showed high anion gap metabolic acidosis with high serum lactate (45.6mg/dl). The serum levels of biotinidase were found to be as low as 10.5 IU (Normal levels >50 IU). Serum ammonia, serum zinc, and sweat chloride levels were found to be normal. Normal levels of amino acids, organic acids, and fatty acids were detected on tandem mass spectrometry. Pure tone audiometry revealed bilateral sensorineural hearing loss.
The differential diagnosis for the periorificial lesions included acrodermatitis enteropathica, essential fatty acid deficiency, cystic fibrosis, and organic acidurias.
Based on the constellation of the above clinical and laboratory findings, a diagnosis of multiple carboxylase deficiency (late-onset) secondary to low biotinidase levels, was made.
The patient was started on a daily oral supplementation of biotin at the dose of 20 mg/day. On the subsequent visit, there was a dramatic improvement in the cutaneous lesions along with regrowth of scalp hair and gradual recovery in the gait. However auditory complaints did not show any resolution. Repeat metabolic profile was found to be within normal limits.
Discussion
Biotin is a water-soluble vitamin that serves as an essential coenzyme for four carboxylases in humans. Biotin-dependent carboxylase catalyzes the fixation of bicarbonate in organic acids and plays a crucial role in the metabolism of fatty acids, amino acids, and glucose. Biotin is also covalently linked to histones and appears to play a role in genomic stability.
Biotinidase, a ubiquitous mammalian cell enzyme, functions to cleave the vitamin biotin from biocytin. The two forms of hereditary multiple carboxylase deficiency are holo-carboxylase synthetase deficiency (neonatal, early-onset) and biotinidase deficiency (infantile, late-onset). The age of presentation varies, ranging from a few weeks after birth up to the age of 8 years depending on whether the deficiency of biotinidase is partial or total.
Clinical features include atopic and seborrheic dermatitis-like eruptions, alopecia, ataxia, hypotonia, developmental delay, sensorineural deafness, and immunodeficiency.[1] The central nervous system pathology in biotinidase deficiency may result from the toxic effect of accumulation in the cerebrospinal fluid of biocytin[2,3] and biotinyl peptides and/or lactate.[4]
Most cases with BD exhibit various metabolic abnormalities like ketolactic acidosis, hyperammonaemia, and organic aciduria. Diagnosis of late-onset BD is confirmed by measurement of enzyme activity in serum. Biotinidase deficiency may be detected on newborn screening[5] or by prenatal molecular diagnosis for mutations, recommended in the case of a previously affected child in the family. A high dose of oral biotin (10-60 mg daily) is advocated for the treatment of BD.
The present case under discussion had an onset of disease at 2 years with perioral and periocular desquamating lesions, alopecia, global developmental delay, ataxic gait, hearing impairment, and recurrent chest infections. The patient was started on biotin supplementation with excellent improvement in cutaneous and metabolic disturbances.
Consent statement
The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but the anonymity cannot be guaranteed.
Financial support and sponsorship
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Conflicts of interest
There are no conflicts of interest.
References
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2. Mukhopadhyay D, Das MK, Dhar S, Mukhopadhyay M. Multiple carboxylase deficiency (late onset) due to deficiency of biotinidase. Indian J Dermatol 2014;59:502–4
3. Wolf B, Grier RE, Allen RJ, Goodman SI, Kien CL, et al. Phenotypic variation in biotinidase deficiency. J Pediatr 1983;103:233–7
4. Suchy SF, McVoy JS, Wolf B. Neurologic symptoms of biotinidase deficiency:Possible explanation. Neurology 1985;35:1510–1
5. Heard GS, Secor McVoy JR, Wolf B. A screening method for biotinidase deficiency in newborns. Clin Chem 1984;30:125–7
