in MPS1H.75 However, progressive pseudoexophthalmos due to shallow orbits has been described in patients with Morquio174 and Hunter syndromes.1

Two different biochemical syndromes are classified as types A and B. The first is due to a deficiency of N-acetyl- galactose-amine-six-sulfatase and the second is due to beta-galactosidase deficiency. These can be detected on the basis of enzyme assay of leukocytes or fibroblasts. The genes for type A is located on chromosome 16q24.3, while that for type B is located on chromosome 3p21.33.

patients may have angiokeratoma corporis diffusum, which is also seen in Fabry disease and fucosidosis.306 Type II sialidosis has also been termed Goldberg–Cotlier syndrome and cherry red spot dementia syndrome; it is the same as mucolipidosis type I. Children become symptomatic between 8 and 15 years of age, with Hurler’s facies, decreased visual acuity, ataxia, myoclonus, mental retardation, corneal clouding, and cherry red spots.84,128 Enlarged viscera and vacuolated blood cells are not found.

Children with this form of MPS have similar physical features to MPS1H. An important feature of Maroteaux–Lamy syndrome is hypoplasia of the odontoid process of the second vertebra, which places these children at risk for spinal cord compression during endotracheal intubation. Intellect may be normal, but skeletal deformities tend to be severe. Corneal clouding is present, and glaucoma may occur. Some children with MPS6 are deaf. The biochemical abnormality is a deficiency in N-acetyl-galactose-amine-four-sulfatase, which is the same enzyme as aryl sulfatase B. The diagnosis can be made by assaying enzyme activity in leukocytes or fibroblasts. These children die in their 20s from cardiac failure. The gene is located on chromosome 5q13–14.

MPS7 (Sls Syndrome)

There is considerable phenotypic variation in this syndrome, but the onset may be in the neonatal period. Intellectual deficiency and motor abnormalities become obvious in the first 2 or 3 years of life. Corneal clouding has been reported in some cases. Dysostosis is a prominent feature, with notable expansion of the ribs and proximal humerus. The biochemical abnormality is a deficiency of beta glucuronidase. The gene for this enzyme is located on chromosome 7q21.11.

Sialidosis

Sialidosis is due to a deficiency of a neuraminidase and occurs in two clinical forms. Individuals with type I sialidosis (cherry red spot myoclonus syndrome) are usually normal into adolescence, when they develop visual deterioration and myoclonus. A cherry red spot in the macula is virtually always present. The visual impairment may be progressive, and intellectual deterioration occurs. Cultured fibroblasts demonstrate a deficiency of aneuraminidase. A concomitant deficiency of beta galactosidase has been described. These

Subacute sclerosing panencephalitis (SSPE) is a chronic, degenerative disease of the CNS that occurs as a rare sequela of measles virus infection. First described by Dawson in 1933,78 it is still not known how the measles virus manages to survive dormant for many years and why it becomes active again and causes SSPE. Although it usually occurs in children who were infected prior to the age of 4, symptoms of SSPE do not develop for many years following the primary infection. Early signs are often subtle and include personality changes, behavioral abnormalities, and declining school performance (phase 1).91 Phase II begins with the onset of involuntary movements, usually an axial myoclonus. Phases III and IV of the disease are characterized by progressive neurological deterioration, severe EEG abnormalities and, usually, coma and death. Rare cases of prolonged survival, stabilization, and improvement have been noted.91,263,266 Neuro-ophthalmologic abnormalities are found in a large number of these patients and include cortical blindness, homonymous hemianopia, visual hallucinations, and impaired visual spatial function. Ocular motor abnormalities are also seen, including nystagmus, supranuclear palsies, and cranial nerve palsies.149,265 Retinal examination may show focal white retinal lesions in the posterior pole that cause loss of central vision. These may produce a cherry red spot appearance when they involve the macu1a. These white lesions resolve into areas of retinal pigment epithelium (RPE) atrophy with gliotic scarring of the retina and radiating retinal folds (Fig. 10.6). There is no evidence of vitreous inflammation during this process. Histopathologically, retinal necrosis is evident with minimal inflammation, and Cowdry type A and Cowdry type B intranuclear inclusions have been recovered from retinal tissue.

Because the neuro-ophthalmologic findings may be the only clinical signs to accompany the behavioral changes early in the disease, recognition of the full spectrum of potential neuro-ophthalmologic dysfunction is important. EEG shows periodic complexes that become more frequent over time. The progression of MR changes shows a consistent pattern.