T. Baykal

We report 32 biotinidase-deficient patients detected by family studies in the index cases. The study group consisted of 10 mothers, 4 fathers and 18 siblings. There were 17 individuals (3 mothers, 4 fathers and 10 siblings) with profound biotinidase deficiency (BD) (< 10% of mean normal activity) and 15 (7 mothers and 8 siblings) with partial BD (10–30% of mean normal activity). In the profound BD group, only three siblings were symptomatic. Dermatitis, microcephaly, developmental delay and convulsions were observed. The patients with partial BD did not have any clinical symptoms except one sibling with borderline IQ score. None of the parents was symptomatic. Family investigation of patients with BD is very important for the detection of asymptomatic patients who are at risk of exhibiting symptoms at any age. Careful evaluation of these untreated individuals with BD is important to obtain additional information about the natural history of this disorder and may provide clues to phenotype–genotype relationships and treatment regimes.

Summary: A patient with a severe neonatal variant of 3‐methylcrotonyl‐CoA carboxylase (MCC) deficiency is reported. The first child of healthy consanguineous Turkish parents presented on the second day of life with dehydration, cyanosis, no sucking, generalized muscular hypotonia, encephalopathy, respiratory depression requiring mechanic ventilation, macrocephaly, severe acidosis and hypoglycaemia. Elevated C₅‐OH‐carnitine in dried blood spot by tandem MS and elevated urinary excretion of 3‐hydroxyisovaleric acid and 3‐methylcrotonylglycine suggested MCC deficiency, confirmed by enzyme analysis in cultured fibroblasts. Cerebral ultrasonography and cranial CT findings revealed progressive changes such as disseminated encephalomalacia, cystic changes, ventricular dilatation and cerebral atrophy. Treatment with high‐dose biotin and protein‐restricted diet was ineffective and the patient died at the age of 33 days with progressive neurological deterioration. Mutation analysis revealed a homozygous mutation in the splice acceptor site of intron 15 in the MCC β‐subunit. Early‐onset severe necrotizing encephalopathy should be included in the differential diagnosis of isolated MCC deficiency.

Summary: Hydroxyproline has the same integer molecular weight as leucine and isoleucine and is quantified with these by tandem mass spectrometry. An infant was diagnosed with hyperhydroxyprolinaemia following further evaluation of an elevated “leucine” level in newborn screening by tandem mass spectrometry.