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Lysosomal storage disorders (LSDs), a heterogeneous group of inborn metabolic disorders, are far more common than most doctors presume. Although patients with a severe LSD subtype are often readily diagnosed, the more attenuated subtypes are frequently missed or diagnosis is significantly delayed. The presenting manifestations often involve the bones and/or joints and therefore these patients are frequently under specialist care by (paediatric) rheumatologists, receiving inadequate treatment. Since effective disease-specific treatments, including enzyme replacement therapy and stem cell transplantation, have become available for certain LSDs and timely initiation of these treatments is necessary to prevent the development of severe, disabling and irreversible manifestations, early diagnosis has become essential. The challenge is to raise awareness for better recognition of the presenting signs and symptoms of LSDs by all doctors who may encounter these patients, including rheumatologists.

A retrospective clinical and biochemical analysis of 41 pediatric patients with cerebral lipidoses seen between 1995 to 2003 was performed at a tertiary referral center for neurologic disorders in southern India. Enzyme assays in serum and leukocytes, including histopathology, neuroimaging, and neurophysiology studies, were performed. There were 20 cases of metachromatic leukodystrophy (infantile,14; juvenile, 6), 12 cases of Tay-Sachs disease (infantile, 9; late G(M2-M3) gangliosidoses, 3), 8 cases of Sandhoff's disease, and 1 male case with multiple sulfatase deficiency. Consanguinity was present in 51.2% of cases. The male-to-female ratio was 23:17. Similar illness in the families was noted in 24.4%. The prominent clinical features in sulfatide lipidoses were regression of motor and mental milestones, seizures, and speech impairment, and in G(M2) gangliosidoses, the features were delayed milestones, startle myoclonus, seizures, and the presence of cherry-red spots. The case with multiple sulfatase deficiency had low levels of arylsulfatase A and B. This study indicates that these autosomal recessive inherited disorders are indeed prevalent in India.

We report a 4-year-old boy with multiple sulphatase deficiency (MSD). His early health was good. By the end of his first year there were concerns about developmental delay but by 26 months he showed clear evidence of regression in that he was barely able to sit unsupported and had lost all fine motor and communication skills. At that time he also had widespread mild ichthyosis that cleared completely with the use of emollients. The neurological deterioration suggested a diagnosis of metachromatic leucodystrophy, and a reduction in the leucocyte arylsulphatase A activity was detected. The ichthyosis suggested steroid sulphatase deficiency, and a reduction in the leucocyte steroid sulphatase activity was detected. The enzyme deficiency was much less marked for steroid sulphatase than for arylsulphatase A in this boy. This diversity in enzyme activities is typical of MSD and correlates with the mild ichthyosis in this child. This case shows that even mild ichthyosis should prompt measurement of steroid sulphatase activity in a child of either sex with unexplained neurological deterioration.

We describe a patient who presented shortly after birth with hyperkinetic behaviour, myoclonia, respiratory insufficiency and hepatosplenomegaly. Gaucher-like storage cells were found in bone marrow. A liver biopsy showed massive lysosomal storage morphologically different to that in known lipid storage disorders. Biochemically, the patient had partial deficiencies of beta-galactocerebrosidase, beta-glucocerebrosidase and ceramidase in skin fibroblast extracts, but the sphingomyelinase activity was normal. Glucosyl ceramide and ceramide were elevated in liver tissue. Loading of cultured fibroblasts with radioactive sphingolipid precursors indicated a profound defect in ceramide catabolism. Immunological studies in fibroblasts showed a total absence of cross-reacting material to sphingolipid activator protein 2 (SAP-2). The patient died at 16 weeks of age. The fetus from his mother's next pregnancy was similarly affected. The possibility that the disorder results from a primary defect at the level of SAP-2 is discussed. We have named this unique disorder SAP deficiency.

Two children with a variant of sphingomyelin lipidosis had otherwise unexplained cirrhosis that was histologically inactive and appeared to run an indolent course. The primary clinical problems involved the central nervous system, with vertical supranuclear ophthalmoplegia being the most distinctive feature. Biochemical analysis of cultured skin fibroblasts obtained from one of the children revealed that sphingomyelinase activity was 42% of control values. The typical inconspicuous hepatic storage and cirrhosis, coupled with the important morphologic finding of sea-blue histiocytes in the marrow, suggested that in cases of unexplained infantile or childhood cirrhosis the marrow should be closely examined for such histiocytes. Likewise, in cases of sea-blue histiocytes without evident etiology, with or without cirrhosis, this disease should be considered.

Detailed behavioral and biochemical investigation of patients with inborn errors of metabolism, especially those intrinsic to the nervous system, may provide many clues to the genetic predisposition underlying human behavioral traits. Relatives of such patients and other individuals with homologous enzymatic lesions due to alleles specifying intermediate activity need to be studied as well. Among the metabolic disorders discussed selectively here, some masquerade as schizophrenia, manic-depressive illness, or hyperactivity syndrome of childhood, providing examples of the striking heterogeneity to be found for these common behavioral disorders.

Thirteen patients with the clinical course of the juvenile type of generalized ceroid-lipofuscinosis were examined clinically, ophthalmologically, neurologically and psychiatrically. This included registration of EEG, x-ray, brain scintigraphy, motor nerve conduction velocity, ERG, fundus photography and bioptical investigations including electron microscopy. The children suffered from progressing decrease of visual acuity, decline of mental capacities, and later on speech and gait disturbances. The most characteristic findings are presented in case reports, two tables and fourteen pictures.

The sphingolipidoses are best defined as lysosomal storage disorders. Their manifestations can be explained on the basis of a few key principles that should all be verified before making a diagnosis. A genetic mutation may reduce the activity of a lysosomal hydrolase. Mutations of the hydrolases, respecting the active site, would not compromise their activity as tested in vitro but might interfere with the lysosomal functions. The undegraded substrates accumulate in the tissues where they are normally synthesized or taken up. The site and rate of storage define the clinical expression of the defect, which may include ataxia. Detailed, comprehensive, multidisciplinary studies emphasize the great complexity of the lysosomal storage disorders and the nonspecificity of single clinical, pathological, ultrastructural, or biochemical criteria. The possibility of inducing storage by chemical means points to aspects of the lysosomal physiology that have been neglected so far but that might also have genetic expression. Lysosomal hydrolases function in a controlled environment dependent on the lysosomal membrane, pH, and hypothetical dispersing agents. Any of these factors conceivably may be genetically impaired and give rise to apparently nonspecific storage.

The occurence of bilateral cherry red spot without neurological disorders is a rare event. The reported case is a girl aged 14 years, whose only complaint was slight deterioration of vision. No secure enzymatic defects was found on examination of leucocytes. Though the cherry red spot is hardly to be explained in another way than by storage in optic ganglion cells. Static perimetry revealed a paracentral depression of contrast sensitivity.

Autopsy findings of a 22-year-old Japanese male who showed the symptoms of both mucopolysaccharidosis and sphingolipidosis are reported. The patient had a gargoyle-like face, bone change with cherry-red spot and absence of mucopolysacchariduria, and moreover accompanied by hereditary thrombocytopathy and color blindness. Autopsy findings were almost the same as those of mucopolysaccharidosis, histochemically and electron microscopically. Unique findings were, however, present in the hepatocytes, another inclusion containing dense fine granuloreticular structures was found electron microscopically. Some foamy cells in the lymph nodes, liver including sinusiodal cells, bone marrow and spleen contained intracytoplasmic sudanophilic substance in the form of moderate electron dense globules by electron microscopy. The outstanding finding of the enzymatic activity was the decrease of beta-galactosidase in the liver and brain.

A cherry-red spot in the macular region of the fundus is the hallmark of the metabolic disorder known as Tay-Sachs disease. Ocular involvement is also a frequent concomitant of generalized gangliosidosis Niemann-Pick disease, and Fabry's disease. Ophthalmologists who are aware of these manifestations are often the first to derive the correct diagnosis in patients with these heritable conditions.

The normal transparency of the cornea permits detailed in vivo study of several human pathologic conditions. Many systemic diseases are associated with corneal dystrophies which are manifested by haziness, opacification, crystalline deposition, or discoloration. Although these abnormal states can sometimes be seen grossly, biomicroscopy with slit lamp illumination is necessary for an exact morphologic description. Only precise delineation can lead to an accurate diagnosis of the corneal disorder and thus provide clues for an associatkd systemic disease.