Diagnostic role of skin or conjunctival biopsies in neurological disorders. An update

Skin biopsy as an aid to diagnosis of disorders of the nervous system without cutaneous manifestations

There are several neurological diseases wherein skin biopsy is useful for diagnosis, even in the absence of skin involvement. Skin biopsy is especially relevant in diseases in which the metabolic error is unknown or has no available diagnostic biochemical test. Skin biopsy, being relatively noninvasive, obviates the need for an invasive procedure such as a brain biopsy. These disorders wherein skin biopsies are particularly useful include the progressive myoclonic epilepsies, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), neuroaxonal dystrophy, and small fiber neuropathies (SFN). We review the role of skin biopsy in such conditions with notes on preferred sites and techniques.

Hybrid gel electrophoresis using skin fibroblasts to aid in diagnosing mitochondrial disease

Objective

We developed a novel, hybrid method combining both blue-native (BN-PAGE) and clear-native (CN-PAGE) polyacrylamide gel electrophoresis, termed BCN-PAGE, to perform in-gel activity stains on the mitochondrial electron transport chain (ETC) complexes in skin fibroblasts.

Methods

Four patients aged 46–65 years were seen in the Metabolic Clinic at Alberta Children's Hospital and investigated for mitochondrial disease and had BN-PAGE or CN-PAGE on skeletal muscle that showed incomplete assembly of complex V (CV) in each patient. Long-range PCR performed on muscle-extracted DNA identified 4 unique mitochondrial DNA (mtDNA) deletions spanning the ATP6 gene of CV. We developed a BCN-PAGE method in skin fibroblasts taken from the patients at the same time and compared the findings with those in skeletal muscle.

Results

In all 4 cases, BCN-PAGE in skin fibroblasts confirmed the abnormal CV activity found from muscle biopsy, suggesting that the mtDNA deletions involving ATP6 were most likely germline mutations that are associated with a clinical phenotype of mitochondrial disease.

Conclusions

The BCN-PAGE method in skin fibroblasts has a potential to be a less-invasive tool compared with muscle biopsy to screen patients for abnormalities in CV and other mitochondrial ETC complexes.

Therapeutic landscape for Batten disease: current treatments and future prospects

Batten disease (also known as neuronal ceroid lipofuscinoses) constitutes a family of devastating lysosomal storage disorders that collectively represent the most common inherited paediatric neurodegenerative disorders worldwide. Batten disease can result from mutations in 1 of 13 genes. These mutations lead to a group of diseases with loosely overlapping symptoms and pathology. Phenotypically, patients with Batten disease have visual impairment and blindness, cognitive and motor decline, seizures and premature death. Pathologically, Batten disease is characterized by lysosomal accumulation of autofluorescent storage material, glial reactivity and neuronal loss. Substantial progress has been made towards the development of effective therapies and treatments for the multiple forms of Batten disease. In 2017, cerliponase alfa (Brineura), a tripeptidyl peptidase enzyme replacement therapy, became the first globally approved treatment for CLN2 Batten disease. Here, we provide an overview of the promising therapeutic avenues for Batten disease, highlighting current FDA-approved clinical trials and prospective future treatments.

Clinical, electrophysiological, imaging, and ultrastructural description in 68 patients with neuronal ceroid lipofuscinoses and its subtypes

PURPOSE

We evaluated the clinical, electrophysiological, imaging, and ultrastructural features of neuronal ceroid lipofuscinoses and its subtypes.

METHODS

The clinical, electrophysiological, imaging, histopathological, and ultrastructural features of 68 (age at onset: 4.3 ± 5.4 years) neuronal ceroid lipofuscinoses and its subtypes (infantile neuronal ceroid lipofuscinoses [9], late infantile neuronal ceroid lipofuscinoses [34], juvenile neuronal ceroid lipofuscinoses [23], and adult neuronal ceroid lipofuscinoses [2] were evaluated. Skin (n = 56), brain (n = 12), muscle (n = 4) and nerve (n = 1) biopsies confirmed the diagnosis.

RESULTS

Clinical manifestations were milestone regression (93%), involuntary movements (92%), seizures (89%), myoclonus (79%), and visual impairment (68%). Response to anticonvulsants was unsatisfactory. Electroencephalography (n = 59) was abnormal in 90%: background slowing (90%); epileptiform discharges (71%), and photoparoxysmal response (4/21). Visual-evoked (n = 33) and somatosensory evoked (n = 40) potentials were abnormal in 62% and 63% of patients. Cranial computed tomography (n = 33) showed diffuse cerebral (61%) and cerebellar (27%) atrophy. Magnetic resonance imaging was abnormal in all 43 patients who were scanned: diffuse atrophy (100%), cerebellar atrophy (40%), leukoencephalopathy (65%), and thalamic T2 W hypointensity (33%). Dermal inclusions such as curvilinear inclusions were the most common abnormality: late infantile neuronal ceroid lipofuscinoses (97%), juvenile neuronal ceroid lipofuscinoses (100%), and infantile neuronal ceroid lipofuscinoses (88%). Additional fingerprint inclusions were noted: juvenile neuronal ceroid lipofuscinoses (43%), late infantile neuronal ceroid lipofuscinoses (15%), and infantile neuronal ceroid lipofuscinoses (13%). Granular osmiophilic deposits were noted in 50% of infantile neuronal ceroid lipofuscinoses. In 75% of patients, there was good correlation between the clinical subtype and ultrastructural inclusion pattern. In 27% of neuronal ceroid lipofuscinoses, multiple inclusions were noted.

CONCLUSIONS

The diagnosis of neuronal ceroid lipofuscinoses should be considered in individuals with characteristic clinical presentations and characteristic ultrastructural dermal inclusions. Three fourths showed morphological correlation of the inclusions with neuronal ceroid lipofuscinoses subtype.

Neuronal ceroid lipofuscinosis with early-onset dementia and periventricular leukoencephalopathy in which a skin biopsy was diagnostically useful

Neuronal ceroid lipofuscinosis (NCL) is a rare disease with onset typically during childhood; however, that developing during adulthood can lead to early-onset dementia. We report a 54-year-old man whose onset coincided with speech impairment, amnesia and dyscalculia. On brain MRI, marked diffuse leukoencephalopathy with periventricular predominance was observed. On a skin biopsy, characteristic fingerprint images were noted, and the patient was diagnosed with NCL. The differential diagnosis of cognitive impairment with leukoencephalopathy is wide ranging; however, when marked symmetrical periventricular-predominant leukoencephalopathy is prevalent and no peripheral neuropathy or gait disorders are evident, a diagnosis of NCL should be suspected and a skin biopsy should be performed.

Progressive myoclonic epilepsy: A clinical, electrophysiological and pathological study from South India

Progressive myoclonic epilepsy (PME) is a syndrome complex encompassing different diagnostic entities and often cause problems in diagnosis. We describe the clinical, electrophysiological and pathological features of 97 patients with the diagnosis of PME evaluated over 25 years. Case records of confirmed patients of Neuronal ceroid lipofuscinosis (NCL = 40), Lafora body disease (LBD = 38), Myoclonic epilepsy with ragged red fibers (MERRF = 10), and probable Unverricht-Lundberg disease (ULD = 9) were reviewed. The mean age at onset in patients with NCL (n = 40) was 5.9+/-9.1 years (M:F:: 28:12). Subtypes of NCL were: late infantile (n = 19), infantile (n = 8), juvenile (n = 11) and adult (n = 2) NCL. EEG (n = 37) showed varying degree of diffuse slowing of background activity in 94.6% and epileptiform discharges in 81.1% of patients. Slow frequency photic stimulation evoked photo-convulsive response in 5 patients only. Giant SSEP was demonstrated in 7 and VEP study revealed a prolonged P100 (2) and absent waveform (7). Electrophysiological features of neuropathy were present in 3 patients. Presence of PAS and Luxol Fast Blue (LFB) positive, auto fluorescent (AF) ceroid material in brain tissue (n = 12) and electron microscopy of brain (n = 5), skin (n = 28) and muscle (n = 1) samples showing curvilinear and lamellar bodies established the diagnosis. Patients of LBD (mean age of onset at 14.4+/-3.9 years, M:F:: 24:14) with triad of PME symptoms were evaluated. EEG (n = 37) showed variable slowing of background activity in 94.6% and epileptiform discharges in 97.4%. Photosensitivity with fast frequency was observed only in 5 patients. CT (n = 32) and MRI (n = 4) revealed diffuse cortical atrophy. Giant SSEP was demonstrated in 24 patients of LBD while VEP study revealed a prolonged P100 (4) and absent waveform (8). Electrophysiological features of neuropathy were present in one patient. Diagnosis was established by the presence of PAS positive diastase resistant, Lugol's Iodine labeled inclusions in sweat glands of axillary skin (n = 35), brain (n = 2) and liver (n = 1). Ten patients with MERRF (mean age at onset: 14.6+/-5.8 years; M: F:: 3:2) had triad of PME symptoms. Muscle biopsy revealed oxidative reaction product and classical ragged red fibers. In nine patients of PME without cognitive decline, probable diagnosis of ULD (mean age at onset: 13.8+/-9.5 years) was considered after biopsy of skin and/or muscle excluded other forms of PMEs. Neuronal ceroid lipofuscinosis and Lafora body diseases were the common causes of PME in the series from south India. This is one of the largest series from the Indian subcontinent to the best of our knowledge. Photosensitivity is notably less common in LBD/NCL in this series distinctly different from those reported in the literature. Further exploration is required to determine whether different genotype is responsible. Morphological changes were helpful in diagnosis and could be confirmed by biopsy of peripheral tissues like skin and muscle in majority (60%). Electron microscopy was helpful in the diagnosis NCL and MERRF.

Fabry disease: an ultrastructural comparative study of skin in hemizygous and heterozygous patients

Fabry disease is a rare X-linked lysosomal storage disorder due to alpha galactosidase A deficiency, better known after the advent of a promising treatment, a periodical enzyme replacement. As other hereditary X-linked disorders, females have historically been considered non-affected carriers, although they are, actually, clinically and pathologically affected to a variable degree. Some women are asymptomatic, but the majority present milder forms of the disease and later onset. This wide range of disease expression is supposed to be related to the levels of enzymatic activity, probably in accordance with a skewing of X inactivation. Lysosomal deposits of ceramide trihexoside have been repeatedly documented in a wide range of tissues, including those found in angiokeratoma, the characteristic cutaneous lesion which allowed the definition of Fabry disease. The aim of this study was to investigate whether there was any difference in the amount of dermal lysosomal storage in males and females, thus accounting for the difference in clinical severity of both groups. For that purpose, with electron microscopy and quantitative methods, we studied the extent of lysosomal deposits in dermal fibroblasts of normal-appearing skin in six females and nine men, enzymatically and genetically proven as to have Fabry disease, and results were compared. Our results indicate a statistically significant difference between the two groups regarding both the percentage of dermal fibroblasts bearing stored material, and the storage surface occupied in 100 fibroblasts per case. We suggest that periodical ultrastructural examination of normal-appearing skin could be an indicator of the efficacy of enzyme replacement therapy and could help to evaluate results.

Neuronal ceroid lipofuscinosis: a clinicopathological study

We report the clinical, electrophysiological, radiological and morphological features in a series of 12 patients of histopathologically confirmed cases (infantile, juvenile and adult onset) of neuronal ceroid lipofuscinosis (NCL) observed from 1979 to 1998 at National Institute of Mental Health & Neurosciences (NIMHANS), Bangalore (South India). The commonest type of NCL was juvenile (n = 8, 67%) while infantile and adult forms were two each (n = 2, 16.8%). The age at presentation ranged from 2 to 45 years (mean--12.6, 14.3 years; median--7 years; M:F ratio of 2:1). Four patients (33%) had positive family history and five patients had history of consanguineous parentage (41.6%). The commonest presenting symptoms were regression of milestones (83.3%) and/or seizures, myoclonus (83.8%) followed by involuntary choreiform movements (50%), visual loss (41.6%), ataxia (33.3%) and abnormal behaviour (16.6%). Neuro-ophthalmological abnormalities like optic atrophy (50%), macular degeneration (33.3%) and retinitis pigmentosa (8.3%) were seen in two thirds. Nerve conduction studies (n = 4) revealed abnormalities in two, suggestive of sensorimotor neuropathy. Scalp EEG (n = 9) showed slowing of background activity (BGA) of varying degrees with paroxysmal bursts of seizure discharges in majority. Cranial CT scan (n = 4) revealed varying degrees of diffuse atrophy. Diagnostic brain biopsy was carried out in 11 and brain was examined at autopsy in 1 case. Histological examination revealed characteristic PAS and Luxol Fast Blue (LFB) positive, autofluorescent (AF) intracellular ceroid material, both in neurons and astrocytes in the grey matter. Electron microscopy (n = 5) revealed curvilinear (n = 4), lamellar (n = 2) and electron dense (n = 2) inclusions in neurons, astrocytes and vascular endothelial cells. To conclude, this neurodegenerative disease had varied but characteristic clinical presentations and required histopathological confirmation of diagnosis.

Noninvasive diagnosis and ophthalmic features of mucolipidosis type IV

OBJECTIVE

To comprehensively describe the ophthalmic characteristics of patients with mucolipidosis type IV.

DESIGN

Prospective natural history study.

PARTICIPANTS

Twenty-two patients with confirmed mucolipidosis type IV. METHODS OR TESTING: External and slit-lamp examination with dilated funduscopy, photography of corneal and retinal lesions, and exfoliative conjunctival cytology were performed.

MAIN OUTCOME MEASURES

Grading of corneal, optic nerve, retinal vasculature, and pigmentary abnormalities.

RESULTS

All patients exhibited some degree of corneal epithelial haze, optic nerve pallor, retinal vascular attenuation, and retinal pigment epithelial changes. The associated ocular findings observed in decreasing order of frequency were strabismus, corneal erosion, cataract, corneal abnormalities, fundus abnormalities, and ptosis. The older patients were significantly more likely to demonstrate severe optic nerve pallor, retinal vascular attenuation, and corneal epithelial haze. Conjunctival cytologic studies showed characteristic lysosomal inclusions on light and electron microscopy.

CONCLUSIONS

Patients with mucolipidosis type IV have characteristic ophthalmic features, most of which have a progressive course. Conjunctival cytologic studies help confirm the diagnosis of this disorder.

Ultrastructural examination of the axillary skin biopsy in the diagnosis of metabolic diseases

There is little information in the literature regarding the usefulness of ultrastructural examination of axillary skin biopsies in the evaluation of metabolic diseases. This is a retrospective clinicopathologic review of 143 patients who underwent axillary skin biopsies as part of evaluations for metabolic disease. Twenty-three (16%) had abnormalities, classified as follows: mitochondrial (n = 12), lysosomal (n = 6), increased glycogen (n = 3), nonspecific cytoplasmic inclusions (n = 2), ceroid lipofuscinosis (n = 1), and intradermal giant cells containing vacuoles and tubular inclusions (n = 1). Muscle biopsies were performed in 13 of the 23 patients; 11 showed abnormalities, including those related to mitochondria (n = 4) and other nonspecific changes (n = 7). Two patients underwent postmortem examination. Follow-up was available in 21 patients. A clinical or biochemical diagnosis was reached in 11 patients: metachromatic leukodystrophy (n = 2), electron transport chain abnormalities (n = 2), glutaric aciduria type II (n = 1), Unverricht disease (n = 1), Lennox-Gastaut syndrome (n = 1), ketotic hypoglycemia of childhood (n = 1), probable Leigh disease (n = 1), 5-methyl tetrahydrofolate homocystine methyltransferase deficiency (n = 1), and pyruvate dehydrogenase deficiency (n = 1). Of the 120 patients with negative skin biopsy results, 29 had abnormal findings on muscle (n = 27), nerve (n = 7), or brain (n = 3) biopsies. One patient had an abnormal heart biopsy result, and 3 patients underwent postmortem examinations. Follow-up was obtained in 27 of 29 patients. Diagnoses were achieved in 15 patients: electron transport chain abnormalities (n = 5), cortical dysplasia (n = 3), myoclonic epilepsy (n = 1), leukodystrophy (n = 2), Pallister-Killian mosaic syndrome (n = 1), Rett syndrome (n = 1), Landau-Kleffner syndrome (n = 1), and mitochondrial cardiomyopathy (n = 1). In conclusion, axillary skin biopsy is helpful in the evaluation of some causes of metabolic disease, but often the findings are nonspecific. A negative biopsy result does not rule out the possibility of metabolic disease, but a positive result may provide direction for further evaluation.

Electron microscopic finding of eccrine sweat gland epithelial cells in a patient with Krabbe disease

A 13 month old boy was found to have severely reduced beta-galactocerebrosidase activity suggesting infantile Krabbe disease. Clinically, the patient showed a progressive neurological deterioration with white-matter disease on radiological study. Axillary skin biopsy was performed to support the diagnosis. On electron microscopy, needle-like inclusions, which are the typical finding seen in the cytoplasm of astrocytes and Schwann cells in the classic infantile form, were present in eccrine sweat gland epithelial cells. This method is useful for diagnosis when nerve biopsy and biochemical analysis are not readily available.

Screening for lysosomal disorders

Patients at any age who develop regression of learned skills, onset of dementia, loss of motor control and organ enlargement should be considered for lysosomal screening. Morphological and biochemical screening methods may reinforce the clinical suspicion, but they are not diagnostic. A widespread use of enzyme assays that appear to be related to the clinical problems is recommended.

Stereological and morphometric analysis of dermal fibroblasts before and after bone marrow transplantation in a case of mucopolysaccharidosis I Scheie phenotype

Bone marrow transplantation (BMT) has been used therapeutically in several types of mucopolysaccharidoses (MPS) and other inherited metabolic disorders. Fibroblasts are severely affected in MPS due to the intralysosomal accumulation of glycosaminoglycans. We report a stereological and morphometric study at light and electron microscopy levels of dermal fibroblasts before and 21 months after BMT in a young girl with MPS I Scheie phenotype (MPS I-S). Dermal fibroblasts showed remarkable morphological changes although their density, expressed as number of fibroblasts per unit volume of dermis (number density), was not modified in the post-BMT samples as compared to pre-BMT ones. Stereological and morphometric parameters referring to cell characteristics of post-BMT fibroblasts (nuclear and cell surface densities, and both nucleus/cell and cell/nucleus volume densities) showed significant differences when compared with pre-BMT fibroblasts, and non-significant differences regarding control cells. On the other hand, quantitative parameters of the lysosomal compartment from post-BMT fibroblasts showed intermediate values between pre-BMT and control fibroblasts. These results, at cellular level, are in agreement with previous biochemical and clinical results, and clearly showed a progressive course to a non-pathological state. All parameters estimated may be considered useful tools in evaluating the success of BMT. These parameters provide quantitative data which can be statistically compared, showing the changes due to the reduction of storage material after BMT. Cell/nucleus volume density is especially interesting since not only is it easy to estimate, even by automatic procedures, but it could also constitute a numerical expression of skin anatomopathological analyses performed post-BMT.

Electron microscopic features of skin in neurometabolic disorders

Skin biopsy may contribute to the clinical diagnosis of neurometabolic disorders. It is an easy and much less traumatic procedure than brain, rectal, peripheral nerve and skeletal muscle biopsies. The method is informative and not too time-consuming for an experienced examiner. Differential diagnosis is possible in most storage disorders since the ultrastructure of the storage is virtually typical in lysosomal and in nonlysosomal diseases. The storage has a particular distribution with characteristic ultrastructural patterns in the various cell types. Skin biopsy plays a major diagnostic role when clinical features are atypical for a storage disorder, to discover new phenotypic variants of known enzymatic deficiencies or when the biochemical defect has not yet been determined. It can be used as a screening procedure to orientate the investigations, to suggest specific biochemical assays on cultured fibroblasts or other tissues or body fluids. It can be applied to detect "presymptomatic" patients in affected families. Other disorders of the nervous system should be investigated in the future to ascertain whether skin biopsies could possibly be used for diagnostic purposes. Thorough knowledge of the morphological features of these disorders may also improve the understanding of their pathogenesis, shed some light on the underlying basic defects and control the results of therapy.

Infantile neuroaxonal dystrophy: diagnosis by skin biopsy

A child who shows progressive motor and mental deterioration after the first year of life, who has pyramidal signs, marked muscle hypotonia, but no seizures, suggests to have infantile neuroaxonal dystrophy (INAD). Beyond the age of two years, the EEG also entails characteristic findings. Diagnosis may be obtained by an ultrastructural examination of biopsied skin. The respective clinical and morphological findings are recorded and illustrated from four patients in this report.

Skin biopsy findings in glycogenosis III: clinical, biochemical, and electrophysiological correlations

Electron microscopy of skin specimens was performed in 4 patients (age range, 7 months-40 years) with glycogenosis III and revealed consistent abnormalities. Massive glycogen storage was observed in epithelial secretory cells of eccrine sweat glands and, less markedly, in smooth muscle fibers from the erector pili. Other cells, including Schwann cells of myelinated and unmyelinated fibers, were not affected. The extent of glycogen storage was similar in all patients and unrelated to age or duration of disease. The extralysosomal nature and selectivity of glycogen deposits, sparing fibroblasts and other cells, differ clearly from the findings in skin from patients with glycogenosis II. The purpose of this study was to show that glycogen deposits in glycogenosis III are not restricted to skeletal muscle and liver, and to assess the usefulness of skin biopsy in this disorder.

Longitudinal clinicoelectrophysiologic study of a case of Lafora disease proven by skin biopsy

A longitudinal clinicoelectrophysiologic study was undertaken of a 15-year 2-month-old girl with Lafora disease who was diagnosed by skin biopsy and an immunohistochemical method with antisera against Lafora bodies. From age 10 years 5 months, 4 months after onset, EEG disclosed progressive deterioration of background activity and incremental increase in epileptic discharges. Photosensitivity was unique: Occipital spikes and diffuse spike-wave discharges were provoked by low-frequency repetitive photic stimuli but without elicitation of myoclonic seizures. Photosensitivity completely disappeared after age 13 years 10 months. High-voltage somatosensory evoked potentials (SEPs) and high-voltage flash visual evoked potentials (F-VEPs) were seen before age 13. After age 13, progressive prolongation of I-III and I-V interpeak latencies of auditory brainstem responses (ABRs), progressive prolongation of latencies of photoevoked eyelid microvibrations, delayed latencies of pattern-reversal visual evoked potentials, and a decrease in the V/I amplitude ratio of ABRs and the previously high F-VEP amplitudes were observed.

Electron-dense lipidic capillary deposits in Rett syndrome

Conjunctival, muscle, and peripheral artery biopsies were examined by light and electron microscopy in a patient with clinically diagnosed Rett syndrome. In capillaries, amorphous and membranous electron-dense deposits were observed (a) endoluminally attached to endothelial cell membranes, (b) within junctional clefts of adjacent endothelial cells, and (c) at abluminal sites of endothelial cells. In addition, electron-dense deposits lay isolated or inside multivesicular bodies in endothelial cells and pericytes. These findings have not been reported before in Rett syndrome. They were not seen in age-matched normal or pathological control cases and are suggested to indicate deposition of an as yet unknown lipidic plasma component possibly in association with impairment of the blood-tissue barrier.

Nerve fibre studies in skin biopsies in peripheral neuropathies. I. Immunohistochemical analysis of neuropeptides in diabetes mellitus

Standardised skin biopsies followed by immunohistochemical examination for the presence of terminal nerve fibres reacting for neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) were evaluated. Healthy subjects regularly displayed free nerve endings of both fibre types in the papillary and reticular dermis. Both fibre types were present close to blood vessels, while CGRP immunoreactive fibres were more often encountered near sweat gland acini compared to SP fibres. Diabetes mellitus complicated by polyneuropathy was accompanied by marked reduction of SP and CGRP reactive fibres in the dermis layers. Five type I diabetes patients without clinical or neurophysiological evidence of polyneuropathy also had reduced density of both fibre types, being significant for CGRP fibres when compared with controls. Skin biopsy with immunohistochemical staining for neuropeptides may represent a sensitive tool in evaluation of patients with peripheral neuropathies.

Diagnosis of Lafora disease by skin biopsy

The Lafora type of progressive myoclonus epilepsy is a rare and fatal familial disease characterized by seizures, myoclonus, and dementia. This diagnosis was confirmed in 2 patients by demonstrating the presence of intracytoplasmic polyglucosan bodies, or Lafora bodies, in the peripheral portion of the eccrine sweat gland duct. Exclusive use of the periodic acid-Schiff stain is recommended for demonstrating these diagnostic inclusions. Electron microscopy reveals fine pale-staining filaments, fine dark-staining granules, and dark-rimmed vacuoles within these non-membrane-bound inclusions. Skin biopsy is the preferred method of confirming the diagnosis of Lafora disease.

Ultrastructural pathology of dermal axons and Schwann cells in lysosomal diseases

Skin tissue specimens, obtained from 60 patients afflicted with a diverse range of lysosomal disorders revealed two groups of lesions within dermal axons, largely unmyelinated ones, particularly within axonal terminals: (1) non-specific mitochondria and dense bodies often enlarging the axonal terminal; and (2) disease-specific lysosomal residual bodies, the latter less frequent depending on the incidence and type of lysosomal disorders, i.e., largely only seen in GM2-gangliosidosis due to hexosaminidase A deficiency and mucolipidosis IV, while the spectrum of lysosomal residual bodies in Schwann cells appeared more variegated, especially due to the occurrence of vacuolar lysosomal residual bodies which were never seen within axons. The most frequent location of abnormal intraaxonal constituents in terminal axons indicates a functionally and morphologically impaired retrograde axonal transport but provides no further evidence as to whether the respective parent nerve cell body has also accumulated lysosomal residual bodies. When studying biopsied skin specimens for diagnosis, axonal terminals beneath the epidermis, about sweat glands, and among smooth muscle cells, ought to be incorporated into a comprehensive electron microscopic examination.

Neuronal ceroid lipofuscinosis. Ocular histopathologic and electron microscopic studies in the late infantile, juvenile, and adult forms

Diagnosis of the neuronal ceroid lipofuscinoses (NCLF), a group of recessively inherited neurolipidoses, must rely on clinical as well as light and electron microscopic histopathologic findings, as a precise biochemical defect has not yet been identified. We have studied the eyes from two patients with the late infantile and juvenile forms of the disease. On electron microscopy, we observed, almost exclusively, inclusions with curvilinear profiles in the late infantile type, while multimembranous and curvilinear bodies were seen in juvenile NCLF. In both forms of the disease, retinal destruction seems to start at the photoreceptor and outer retinal levels and progresses from the macular area to the periphery. Conjunctival biopsy is helpful in the diagnosis of these disorders, as demonstrated in the adult case presented here.

The inherited neurodegenerative disorders of childhood: clinical assessment

This review represents an examination of four groups of neurodegenerative diseases, namely the sphingolipidoses, the adrenoleukodystrophy complex, the neuronal ceroid lipofuscinoses, and the sialidoses/sialuria complex. Using a combination of clinical assessment, neuroradiologic appearance, and clinical neurophysiology, one may develop strategies that lead to specific chemical or biochemical determinations for specific diagnoses. In general, disorders of white matter may be distinguished from disorders of gray matter by their appearance on computed tomography and by abnormalities of nerve conduction velocities and auditory brain stem responses. In contrast, disorders of gray matter may be distinguished from disorders of white matter by their appearance on computed tomography and utilization of electroretinography, visual evoked responses, and, to a lesser extent, EEG findings. Where necessary, skin, conjunctival, or nerve biopsy may prove to be useful adjuncts to the diagnosis. Presently, treatment depends on prevention, although aggressive efforts are under way to establish corrective therapy by enzyme replacement. To this end, the use of already existing animal models may prove to be helpful.

Lysosomal storage in human skeletal muscle

Skeletal muscle is involved symptomatically in two lysosomal storage diseases, acid maltase deficiency and a similar condition in which enzyme levels are normal. Asymptomatic storage in skeletal muscle cells is found in Batten-Kufs' disease (ceroid lipofuscinosis), Fabry's disease, and mannosidosis, as well as in rare patients with an unidentified storage disease. Other cell types (vascular endothelium, smooth muscle, fibroblasts, satellite cells) within the confines of the biopsy specimen may reveal storage in other diseases. The differential diagnosis involves predominantly both normal and abnormal conditions in which acid phosphatase activity is prominent in cells.