Neuronal ceroid lipofuscinosis: diagnostic algorithm and clinical description of the variants late infantile Finnish (CLN5) and Turkish (CLN7)

Introduction. The neuronal ceroid lipofuscinosis are classified based on age at onset into four main clinical forms in childhood: infantile, late infantile, juvenile and congenital (CLN1, CLN2, CLN3 and CLN10). The variant late infantile forms (CLN5, CLN6, CLN7 and CLN8) are characterized by a wide variability of the clinical phenotypes and the most patients are originated from Finland and Turkey (Finnish, CLN5, and Turkish, CLN7 variants). Case reports. We describe three unrelated patients with Finnish variant and another patient with Turkish variant. We describe an algorithm to facility the diagnosis of these low prevalence diseases. Patients with Finnish variant started with behaviour disorder between 2.6 and 4.6 years of age followed by learning difficulties and visual failure at an age of 6 years. Generalised tonic-clonic and myoclonic seizures were observed at 7 years of age with myoclonic jerks later on. Patients developed ataxia and blindness within 9 years and increasingly disability at 11 years of age. The patient with Turkish variant started with refractory epilepsy at age of 2, followed by a severe neurodegeneration manifested by ataxia, loss of walking ability within 2-3 years and vegetative state at 11 years of age. Conclusions. The clinical spectrum of the variant late infantile forms shows a wide geographical distribution. We report three novel mutations in the CLN5 gene and a diagnostic algorithm to facility the correlation genotype-phenotype studies.