Kearns syndrome: a heterogeneous group of disorders with CPEO, or a nosological entity?

In connection with 4 new cases of Kearns syndrome (multisystem form of mitochondrial CPEO), the condition was found to be present in slight to oligosymptomatic form in all 4 families. The marker symptom in subclinical patients was nearly always ptosis (sometimes very slight) and occasionally diabetes. In the literature other endocrine disorders, retinal anomalies, deafness, growth disturbances, etc., have been noted as subclinical symptoms in former generations. Heredity appears to be autosomal dominant in these 4 families, with very variable expressivity. The possibility that one gene is responsible for the disease seems to be plausible, but the marked variation in expressivity suggests a modifying influence of other alleles; in this sense, therefore, one may speak of multifactor inheritance. Supporting facts could also be found in the literature, where there was autosomal dominant heredity of the disease-carrying gene, but for its complete expression 'amplifying' factors (alleles) were needed. The pleiotropia of the disease-carrying gene is explained by a mitochondrial disorder of various organs. On the basis of the heredity, therefore, Kearns syndrome is not a syndrome but a disease. The most serious, most progressive and most extensive (multisystem) variant of Kearns disease is the infantile form, known as the 'Kearns-Sayre syndrome. When the expressivity of the disease is less extensive it usually occurs later in life and is less progressive: the adult form of Kearns disease.