E ditor—The hereditary spastic paraplegias are characterised by progressive spasticity, predominantly affecting the lower limbs. They have been divided into “pure” or complicated forms. 1, 2 Four loci for autosomal dominant pure hereditary spastic paraplegia (ADPHSP) have been mapped, on chromosomes 2p (SPG4), 8q (SPG6), 14q (SPG3), and 15q (SPG6). 1-3

Cognitive impairment may be present in apparently “pure” hereditary spastic paraplegia. Tedeschi et al 4 found subclinical cognitive deficits in seven patients with autosomal recessive or autosomal dominant pure hereditary spastic paraplegia, when compared to normal, unrelated controls. Webb and Hutchinson 5 investigated 31 patients from 12 kindreds with ADPHSP (loci not described) and found subclinical cognitive impairment, apparently restricted to cases over 50 years old. In addition, the description of an SPG4 linked family with paraplegia complicated by subcortical dementia suggests that “pure” hereditary spastic paraplegia and hereditary spastic paraplegia complicated by frank dementia may be allelic disorders. 6