HOW WILL BIOTINIDASE DEFICIENCY AFFECT MY CHILD?

Without Treatment
Without biotin therapy, children with biotinidase deficiency may develop one or more of the symptoms shown in Table 1.

Table 1. Frequency of Clinical and Biochemical Symptoms in 83 Children with Biotinidase Deficiency Prior to Treatment

Percentage of Affected Children	Symptom
>50%	Alopecia (hair loss) Developmental delay Hypotonia (poor muscle tone) Ketolactic aciduria Seizures Skin rash/skin infection
25-50%	Ataxia (poor coordination) Conjunctivitis (redness of the eye) Hearing loss Lethargy (drowsiness) Mild hyperammonemia Breathing problems Eye problems
10-25%	Coma Feeding difficulties/vomiting/diarrhea Fungal infections
<10%	Hepatomegaly (enlarged liver) Speech problems Splenomegaly (enlarged spleen)

Symptoms usually appear between three to six months of age, but may appear as early as one week of age or as late as ten years of age. The number of symptoms that a child develops and the severity of the disorder vary from child to child, even within the same family.

Early symptoms of biotinidase deficiency often include seizures of various types, particularly myoclonic seizures, and hypotonia (poor muscle tone). These symptoms are not specific to biotinidase deficiency, therefore, a diagnosis is not usually made immediately. Other early symptoms include breathing problems, such as tachypnea (fast breathing), hyperventilation (fast, shallow breathing), stridor (difficulty moving air through the windpipe), and apnea (long pauses in breathing); skin rashes often called seborrheic or atopic dermatitis; partial or complete alopecia (hair loss); and conjunctivitis (redness of the eye). Ataxia (poor coordination or clumsiness) and developmental delay usually occur later. The immune system also appears to be altered, and fungal and bacterial infections can occur in untreated children. Hearing loss is usually sensorineural (involves the nerve to the ear) and a variety of eye problems, especially optic atrophy (small optic disk that can cause loss of vision), may develop. Abnormal substances often accumulate in the urine (organic aciduria) and in the blood (ketolactic acidosis and hyperammonemia). These biochemical abnormalities may cause damage to important organs like the brain, skin, inner ear, and eyes and may be life threatening. Some untreated infants and children have died from this disorder.

Unrecognized and untreated biotinidase deficiency has also been considered as one possible cause of sudden infant death syndrome (SIDS), although more information is needed in this area. If you have experienced such a loss, you may wish to discuss it again with your doctor. A careful review of your baby's medical records may provide evidence that your baby had experienced symptoms of unrecognized biotinidase deficiency.

With Treatment
All children who have developed symptoms of biotinidase deficiency have improved when treated with recommended doses of biotin. The biochemical abnormalities, seizures, muscle tone, and skin rash usually show rapid improvement. Hair begins to grow back over a period of weeks to months. Other symptoms including hearing loss, visual impairments, and developmental delay are not always corrected by treatment, but they usually do not get worse. This may be because organs are damaged prior to treatment or possibly because high levels of substances such as biocytin are present even after treatment has begun. With proper treatment, biotinidase deficiency is not a life threatening condition.

(photos before and after treatment)

Infants and children treated before symptoms appear usually do not develop any symptoms of this condition.

BEFORE BIOTIN TREATMENT	AFTER BIOTIN TREATMENT
BEFORE BIOTIN TREATMENT	AFTER BIOTIN TREATMENT

 

By permission of McGraw-Hill Information Services. 
The Metabolic Basis of Inherited Disease. Sixth Edition.
p.2094 (1989) and N. Engl. J. Med. 304: 817 ( ).

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