Hereditary spastic paraparesis with distal muscle wasting, microcephaly, mental retardation, arachnodactyly and tremors: new entity?

We present a consanguineous Pakistani family in which four patients (two males and two females) had a new Troyer-like phenotype. All four patients showed some marfanoid features (span more than height, arachnodactyly, high arched palate), and generalized hyper-reflexia. The two affected males and the younger female also had microcephaly and mental retardation. Features only present in the affected males included short stature, dysarthria, amyotrophy of the distal muscles, fasciculations and tremor. The distal muscle wasting in the two affected brothers reflected the presence of axonal neuropathy demonstrated both electrophysiologically and by nerve biopsy. Although neither of the sisters had any degree of distal muscle wasting, both had reduced M-wave amplitude of the tibial and peroneal nerves, bilaterally. The described phenotype does not fit any of the recognized forms of hereditary spastic paraparesis with distal muscle wasting. The specific axonal neuropathy differentiates it from familial motor neuron disease with mental retardation. The reported phenotype represents a possible new Troyer-like syndrome similar to that described by Neuhäuser (1976), but differs from it by the lack of major dysmorphic features.