Progressive spastic paraplegia as a feature of tetrasomy 18p

Abstract

The tetrasomy 18p or isochromosome 18p [i(18p)] syndrome isassociated with moderate to severe mental retardation, microceph-aly, dysmorphic features, and other abnormalities. ‘‘Spasticity’’ or‘‘hypertonia’’ are frequently reported [about 80% of cases, Swingleet al., 2006], but not clearly defined; such definition is, however,essential in singling out the different nervous structures/pathwaysinvolved in the disorder.Herewepresentacaseinwhichwedeterminedthatspasticitywasdue to a progressive spastic paraparesis, with the involvement ofcortico-spinal and afferent somatosensory pathways. The clinicalpicture of this patient fits the basic features of genetic (orhereditary) spastic paraplegias (GSP), which are due to at least30 different genetic loci, to date none identified in 18p (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book¼genep QIV<40, QIP<40), without behavioral problems.Physical examination reveals microcephaly (49cm, significantlybelowthe2SD;meanvaluesforage54cm),shortstature(140.5 cm, 2,5 SD), weight 28.2 kg ( 1.93SD). He has spastic paraparesis:bilateral hypertonic adduction of hips with equinovarus feet moresevere at left, generalized tendon hyperreflexia and bilateralBabinski. He walks with tip-toe initial foot contact and slight hipadduction (gait had improved after botulinum toxin injection inthe gastrocnemius muscles). Fingers of the hands are also in slightflexor hypertonus and dexterity of hand-finger movement is re-duced. Vibratory sensation is preserved. Bladder disturbances arenot reported.Dysmorphicfeatures(Fig.1)includedlowanteriorhairimplant,ovalfacialshape,downslantingpalpebralfissures,pointednasaltip,high nasal bridge, long philtrum, small mouth with protrudinglower lip, teeth malocclusion, high palate, low-set small ears,tapering fingers, clinodactyly, camptodactyly, kyphosis, micro-penis (3cm), bilateral cryptorchidism, with normal left and verysmall right testicle at abdominal ultrasound examination. Thecardiac investigation revealed ostium secundum interatrial defect.Nootherabnormalitiesofviscerawerefound.Heneverhadseizuresand denied bladder problems.The somato-sensory potentials (SSEPs) evoked by the stimula-tion of the tibial nerves showed an absence of the cortical responseN35 in response to the stimulus at left, and an increased latency(47msec) at right, with normal lumbar responses bilaterally. Stim-ulation of median nerves gave normal responses. Brain MRI, EEG,auditory and visual evoked responses were normal.