Homocarnosinosis. Homocarnosinase deficiency.
Incidence
Inheritance in the reported family seems to be autosomal dominant. Only 4 cases reported in one single family.
Clinical Characteristics
Homocarnosinosis is an extremely rare metabolic defect that has been reported in only one family, namely a woman and three among her children. The latter showed progressive spastic diplegia, mental retardation and retinitis pigmentosa but their mother was symptom free. It is therefore uncertain whether there is a relationship between the biochemical defect and the clinical symptoms. Inheritance in the reported family seems to be autosomal dominant. Homocarnosine is a brain-specific dipeptide of gamma-aminobutyric acid (GABA) and histidine. Sjaastad et al. (1976) found the substance elevated to levels about 20 times normal in 2 brothers and a sister. All 3 had progressive spastic paraplegia, mental retardation and retinal pigmentation. The mother was clinically normal but had elevated CSF homocarnosine in a range even higher than that of the affected children. The elevation of CSF homocarnosine in this disorder is attributable to serum carnosinase deficiency. Diagnosis is made by aminoacid exam of CSF.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Diagnosis is made by aminoacid exam of CSF. There is elevation of CSF homocarnosine in this disorder.