Two children, an 8-year old boy and a 6-year old girl, with progressive ataxia, dysmetria, hypoactive or absent deep tendon reflexes, equivocal plantar response, and sensory impairments, were investigated by pathologists and neurologists at the University of Vermont, Burlington, VT, and University of Saskatchewan, Saskatoon, Canada. The diagnosis of SCD was established by the clinical course and laboratory tests that were normal for arylsulfatase, amino acids, phytanic acid etc.
Rectal biopsy specimens were examined ultrastructurally by electron microscope and by a laser microprobe mass analyzer (LAMMA). Clusters of acicular osmophilic inclusions in the mitochrondria of neuronal somata were consistent with crystals of calcium hydroxyapatite (CHA). The calcific nature of the deposits was confirmed by LAMMA. Similar mitochrondrial inclusions were found in 10% of smooth muscle cells but not in skeletal muscle and nerve biopsy specimens. Tissue from control subjects had no mitochrondrial acicular deposits. It has been suggested that the calcium overload may interfere with mitochondrial enzyme activity by disrupting oxidative phosphorylation. 
COMMENT: An abnormal oxidative phosphorylation in muscle mitochondria of patients with Freidreich’s ataxia (FA) was previously demonstrated by Stumpf DA et al ; mitochondrial malic enzyme activity was 10% of control level in FA fibroblasts. Also, glutamate dehydrogenase deficiency has been noted in cultured skin fibroblasts and leukocyte homogenates of patients with spinocerebellar syndrome . These studies and the present report may eventually lead to carrier detection and possible specific therapies for spinocerebellar degenerative disease.