Mucolipidosis II (I-Cell Disease): Ultrastructural Observations of

Mucolipidosis II (I-cell disease):Ultrastructural observations of conjunctiva

and skin

Kenneth R. Kenyon and Judith A. Sensenbrenner

Conjunctival and skin biopsies from a 25-monih-old patient with mucolipidosis II (I-cell disease)were studied by electron microscopy. In both tissues the subepithelial connective tissue wasmarkedly hypercellular, as histiocytes and fbroblasts showed extensive vacuolation by singlemembrane-limited inclusions with fbrillogranular and membranous lamellar contents. TheSchwann cells and axonal processes of peripheral nerves and the vascular perithelial cells weresimilarly affected. Histochemical and ultrastructural evidence indicates that these storagevacuoles may be derived from lysosomes which contain excessive amounts of acid mucopoly-saccharide and glycolipid. Biomicroscopically visible granularity of the corneal stroma suggeststhe accumulation of these storage substances also within the cornea. Symmetrically enlargedcorneas were also present.

Key words: I-cell disease, mucolipidosis, mucopolysaccharidosis, sphingolipidosis,acid mucopolysaccharide, glycolipid, sphingolipid, megalocornea,

corneal clouding, ultrastructure, conjunctiva and skin, lysosome,fibrillogranular vacuole, membranous lamellar vacuole

TJU

.he mucolipidoses (MLS's) are a newlycategorized group of inherited metabolicstorage diseases which seemingly occupy

From the Eye Pathology Laboratory, WilmerOphthalmological Institute, and the MooreClinic of The Johns Hopkins Hospital, Balti-more, Md.

Supported in part by Public Health Service Post-doctoral Fellowship 1 F02 EY 48611-01 fromthe National Eye Institute (Dr. Kenyon).

Presented at the Spring Meeting of the Associa-tion for Research in Vision and Ophthalmology,April 26 to 30, 1971, Sarasota, Fla.

Reprint requests to: Dr. Kenneth R. Kenyon, EyePathology Laboratory, The Johns HopkinsHospital, 601 North Broadway, Baltimore, Md.21205.

Manuscript submitted June 11, 1971; manuscriptaccepted June 29, 1971.

an intermediate position between the muco-polysaccharidoses and the sphingolipidoses.1

The ten disorders currently included inthis group are listed in Table I.

Clinically, these disorders share manyfeatures of the mucopolysaccharidoses(MPS's), including coarse facial features,skeletal dysplasia, and mental retardation(Table II). Biochemically, however, theMLS's resemble the sphingolipidoses (SLS's)with respect to normal urinary excretionof acid mucopolysaccharide (AMP) andvisceral storage of glycolipid and/orsphingolipid in addition to AMP. The sig-nificant ocular manifestations of the MLS'sare also common to both the mucopoly-saccharide and sphingolipid disorders.These ocular features are variable and in-clude corneal clouding (in generalized

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556 Kenijon and Sensenbrenner Investigative OphthalmologyAugust 1971

Fig. 1. Light photomicrograph of the conjunctiva shows connective tissue cells with vaciiolatedcytoplasm (asterisks) to be most numerous in the collagenous stroma (C) which underlies theconjunctival epithelium (E). (Paraphenylenedianiine, phase contrast, x800.)

Table I. Classification of the mucopolysaccharidoses (MPS's), mucolipidoses(MLS's), and sphingolipidoses

Mucopolysaccharidoses Mucolipidoses Sphingolipidoses

MPS I (Hurler)MPS II (Hunter)MPS III (Sanfilippo)MPS IV (Morquio)MPS V (Scheie)MPS VI (Maroteaux-Lamy)

Generalized gangliosidosis(Gjii-gftngliosidosis I and II)

FucosidosisMannosidosisJuvenile sulfatidosis, Austin typeMLS I (lipomucopolysaccharidosis)MLS II (I-cell disease)MLS III (pseudo-Hurler polydys-

trophy)Farber's diseaseSea-blue histiocyte syndrome

'(chronic Niemann-Pick disease)

Tay-Sachs disease (G11 .-gangliosidosisI)

Sandhoff's disease (Gus-gangliosidosisID

Niemann-Pick diseaseGaucher's diseaseFabry's diseaseKrabbe's diseaseInfantile metachromatic leukodys-

trophyLactosyl ceramidosis

gangliosidosis, MLS I, and MLS III) andmacular cherry-red spot (in generalizedgangliosidosis, MLS I, and Farber's dis-ease ).

MLS II, the I-cell variant, is a rare dis-order which was first described in 1967 byLeroy and DeMars,2 who found coarsecytoplasmic inclusions in cultured fibro-blasts (which they designated I-cells orinclusion cells) from two children with

this disease. At present, only about tencases have been reported.10 On the basisof these reports, MLS II may be char-acterized as an autosomal recessive traitwhich is present at birth and is associatedwith severe psychomotor retardation, earlycessation of growth, Hurler-like facies withcharacteristic gingival hyperplasia, and ex-treme skeletal dysplasia. Additional clinicalsigns include mild hepatic enlargement,


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Mucolipidosis II: I-cell disease 557

Fig, 2. Light photomicrograph of the skin reveals many vacuolated histiocytes (asterisks) in thesuperficial dermis. E, epidermal cells; C, collagenous dermis. (Paraphenylenediamine, phasecontrast, xl,000.)

Table II. Comparative features of the mucopolysaccharidoses, mucolipidoses,and sphingolipidoses (after Spranger and Wiedemann1)

Mucopolysaccharidoses Mucolipidoses Sphingolipidoses

Gargoyle-like faciesSkeletal dysplasiaMental retardation (variable)Abnormal mucopolysacchariduriaVisceral storage of AMP

Ocular features (variable)Corneal cloudingRetinal pigmentary degenerationOptic atrophy

Gargoyle-like faciesSkeletal dysplasiaMental retardation (variable)Normal mucopolysacchariduriaVisceral storage of AMP and gly-

colipids

Ocular features (variable)Corneal cloudingMacular cherry-red spot

No gargoyle-like faciesNo skeletal dysplasiaMental retardationNormal mucopolysacchariduriaVisceral storage of glycolipids

Ocular features (variable)Corneal cloudingMacular cherry-red spot

restricted joint mobility, and unusually tightskin. Corneal opacities have been describedin only one case of probable MLS II,6 andmacular cherry-red spot has never beenreported.

Laboratory findings include vacuolatedlymphocytes and bone marrow cells andnormal urinary excretion of AMP. The re-fractile cytoplasmic inclusions in culturedfibroblasts are periodic acid-Schiff (PAS)and Sudan black positive* and, followingtreatment with chloroform-methanol, are

metachromatic with toluidine blue' therebyindicating storage of both glycolipids andAMP.

The pathogenesis of MLS II is as yetunclear. Biochemical studies of I-cell tis-sues and cultured cells are not in completeagreement; however, decreased activity ofbeta galactosidase is the most consistentfinding to date.1"3' 5'7

To our knowledge, the histopathology ofMLS II has not been previously reported.Thus, the present ultrastructural study of


558 Kenyon and Sensenbrenner Inoestigotioe OphthalmologyAugust 1971

Fig. 3. In the superficial stroma of the conjunctiva, histiocytes and fibroblasts are numerous.The cytoplasm of these cells shows an alveolar reticulated appearance, as abnormal storagematerial (asterisks) has distended the cells, displaced their nuclei (N), and seemingly excludedother cytoplasmic organelles. E, epithelium; C, collagenous connective tissue. (x5,400.)

conjunctiva and skin from a patient withI-cell disease is presumably the initial histo-pathologic description of this disorder.

Case reportThe patient (JHH 140 25 75) was the 25-

month-old son of unrelated Caucasian parents. Fol-lowing an unremarkable pregnancy and delivery,coarse facies and inguinal hernias were noted, andsubsequent psychomotor development was ex-tremely slow. In November, 1970, physical ex-amination revealed an alert but otherwise severelyretarded child with the facial and skeletal stigmata

of I-cell disease. The liver was enlarged to 8 cm.below the right costal margin and a spleen tip waspalpable. Everywhere on his body, the skin wassmooth, tight, and thickened.

Ophthalmic evaluation disclosed that the childfollowed objects and fixated well in all fields ofgaze. There was neither strabismus nor nystagmus.The pupils were round, regular, and reactive tolight. External examination was normal except foran increased corneal diameter of 12.5 mm. bilater-ally. The corneas appeared grossly clear butshowed diffuse fine stromal granularity by slit-lamp examination. Intraocular pressures were 13.0mm. Hg (Schi^tz) bilaterally on two occasions.


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Fig. 4. At higher magnification, the cytoplasm of a conjunctival histiocyte (area indicated bylarge asterisk in Fig. 3) is filled by an alveolar rericulum of unit membranes (each — 60 Ain thickness; arrows) interspersed with fibrillogramilar material (asterisk) and membranousmaterial arranged as concentric (white circle) or parallel (black circle) lamellae. (*83,500.)

Dilated pupil funduscopy was entirely withinnormal limits; specifically, the disc and vessels ap-peared normal, and neither macular cherry-redspot nor retinal pigmentary change was evident.

Laboratory studies showed metachromaticallyvacuolated lymphocytes, normal bone marrow, andnormal mucopolysacchariduria. Skeletal x-raysshowed severe dysostosis multiplex.1

Materials and methods

Biopsies of inferior bulbar conjunctiva and an-terior abdominal skin were obtained under generalanesthesia and immediately processed for histo-chemical study and electron microscopy.

For histochemistry, frozen unfixed sections ofskin were stained with toluidine blue, Alcian blue,PAS, oil red O, Sudan black, aldehyde fuchsin,acid phosphatase, glucuronidase, and ribonuclease.

For electron microscopy, conjunctival and skinspecimens were fixed in two per cent osmiumtetroxide (buffered with 0.14M veronal acetate,pH 7.3, 280 milliosmolar) for 20 minutes at 0°C. and for one hour at room temperature. Thesetissues were then dehydrated in graded alcohols,embedded in Araldite epoxy resin, and sectionedon a Porter-Blum MT-2 ultramicrotome. Fororientation and light photomicrography, thick sec-tions (•—> 1 p) were stained with paraphenylene-diamine. Thin sections were stained with uranyl

acetate and lead citrate and were examined witha JEM 100-B electron microscope.

Results

Histologic examination of the conjunc-tiva revealed the accumulation of largemononuclear histiocytes with foamy cyto-plasm in the superficial stroma (Fig. 1).Similar cells in the deeper conjunctivalconnective tissue were also distended byfine cytoplasmic vacuoles. In the superficialderm is of the skin, cellular vacuolationwas equally impressive (Fig. 2).

Histochemical studies of the skin demon-strated connective-tissue cells which stainedpositively for acid mucopolysaccharide bythe Alcian blue technique. These cells,however, did not show toluidine blue meta-chromosia (although chloroform-methanolextraction was not attempted) and did notstain with PAS, lipid. stains, or lysosomalenzyme stains.

By electron microscopy, numerous bal-looned histiocytes were especially strikingin the superficial stroma of the conjunctiva


560 Kenyon and Sensenbrenner Investigative OphthalmologyAugust 1971

Fig. 5. In some conjunctival histiocytes, membranous lamellae form elaborate myelin-like con-figurations (circled) with — 55 A periodicity and characteristic splitting of the dense band(arrows). (x90,000.)

(Fig. 3). The cytoplasm of these cells waspacked with abnormal material which oftenexcluded all other organelles except thenucleus. Discrete intracellular vacuoleswere seldom evident; rather, rupture andcoalescence of vacuoles had apparentlyproduced an alveolar reticulum of mem-branous material. At higher magnification,the storage material was seen to be com-posed of sparse, fine, granular substanceand of membranous inclusions arranged asparallel or concentric lamellae (Fig. 4).

Frequently, these membranous lamellarinclusions assumed elaborate myelin-likeconfigurations in which a characteristicperiodicity of 50 to 60 A could be resolved(Fig. 5). In the deeper conjunctival stroma,connective tissue cells were also extensivelyinvolved (Fig. 6), but there the abnormalstorage inclusions retained their integrityas discrete, single membrane-limited vac-ules which contained predominantly fibril-logranular material (Fig. 7). In these cells,membranous lamellar vacuoles, lipoid


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Fig. 6. In the deeper conjunctival stroma, connective tissue cells are filled with discrete storagevacuoles (measuring ~ 0.5 to 1.0 M in diameter). N, nucleus; C, collagen. {x7,700.)

globules, and polymorphous electron-denseinclusions were less prominent than in thesubepithelial connective tissue cells.

In the skin, histicytes and fibroblasts ofthe superficial dermis displayed vacuolationwhich was identical to that of the con-junctival connective tissue cells (Fig. 8).

In both conjunctiva and skin, theSchwann cells and axonal processes ofperipheral nerves showed these samevacuolar changes (Figs. 9 and 10). Theepithelial cells of the conjunctiva and theepidermis were seemingly unaffected. The

vascular endothelium of the lymphaticsand capillaries was also not involved, butperithelial cells of the capillaries consistent-ly contained prominent storage vacuoles(Fig. 11).

In both tissues, neither extracellularvacuoles nor abnormal accumulations ofextracellular material were discernible byelectron microscopy.

Discussion

In our patient with MLS II and in pre-vious studies of the MLS's, the findings



Fig. 7. At higher magnification, the cytoplasm of a conjunctival fibroblast, similar to thoseillustrated in Fig. 6, is seen to contain vacuoles which are limited by single unit membranes(each ~ 60 A in thickness; arrows) and which contain predominantly fine fibrillogranularmaterial. <x85,0O0.)

suggest that both AMP and glycolipidsare the abnormally accumulated substancesin these storage diseases.

Histochemical evidence for combinedstorage of AMP and glycolipid in MLS IIis afforded by the aforementioned work ofLeroy and associates3 and of Matalon andco-workers.4 Both groups found positivestaining with PAS and Sudan black andmetachromasia with toluidine blue in cul-tured I-cells, which also showed an in-creased content of AMP and glycolipid bydirect biochemical assay.4 These findingsare entirely consistent with observations ofliver tissue from the present patient inwhich hepatic reticuloendothelial cells heldSudan black-positive material, which byelectron microscopy proved to be large

lipoid or membranous lamellar inclusions.5

In generalized gangliosidosis, visceral his-tiocytes have also been shown to containstorage mater-ial which was PAS positive,weakly sudanophilic, and weakly toluidineblue metachromatic,9 whereas in the oculartissues affected by this disorder, vacuolatedhistiocytes demonstrated an increased AMPcontent by the colloidal iron reaction.10

Similarly, in mucolipidosis III (pseudo-Hurler polydystrophy), :Alcian blue stain-ing of skin fibroblasts11 and toluidine bluemetachromasia of conjunctival connectivetissue cells12 have also indicated an ab-normal accumulation of AMP.

In the MPS's, wherein AMP storage pre-dominates, electron microscopy revealsstorage vacuoles with predominantly fibril-


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Fig. 8. In the skin, histiocytes of the superficial dermis show extensive vacuolation by singlemembrane—limited vacuoles which contain fibrillogranular material and membranous lamellae(asterisks). Inset, Two membranous lamellar vacuoles (extreme right of figure) are shown athigher magnification. E, epithelial cell; BM, basement membrane of epidermis; C, collagenousconnective tissue; N, nucleus. (*8,750; inset, x40,000.)

logranular contents (see Discussion, ref.13), whereas in the SLS's, membranouslamellar vacuoles have been shown to con-tain glycolipid (see Discussion, refs. 12and 14). Ultrastructural studies of a varietyof tissues affected by MLS's have consist-ently disclosed large numbers of bothfibrillogranular and membranous lamellarvacuoles.10'12'1517 And for MLS II, in par-ticular, the cellular defect appears to bevirtually a composite picture of the MPS'sand SLS's. Thus, the simultaneous occur-rence of both vacuolar types in the MLS'sconstitutes strong morphologic evidence forthe accumulation of both AMP and glyco-lipid in these disorders and additionallyattests to their intermediate position be-tween the MPS's and the SLS's.

The concept of lysosomal diseases, firstintroduced in 1964 by Van Hoof and Hers,18

has subsequently been applied to those

metabolic disorders (including the MPS'sand SLS's) in which storage substances arethought to accumulate within lysosomes,the impaired or deficient hydrolytic en-zymes of which render these substances in-digestible. Reports of significantly de-creased activity of one or more of theacid hydrolases in tissues of MLS II pa-tients2' 5"7 are consistent with the possibilityof a lysosomal disorder in this disease.Additional histochemical studies of cul-tured I-cells have also revealed increasedactivity of the lysosomal enzyme, acidphosphatase, an observation which suggeststhat the I-cell inclusions may be activatedlysosomes.2 This finding was also especiallystriking in the liver biopsy specimen of thepresent patient, wherein focal epitheloidcell granulomas showed markedly increasedhistochemical staining for acid phosphatase,which by electron microscopy proved to


564 Kenyon and Sensenbrenner Inoestigative OphthalmologyAugust 1971

Fig. 9. The Schwann cell of a conjunctival nerve contains numerous intracytoplasmic vacuoles.Inset, Higher magnification of vacuole (indicated by asterisk in figure) shows its single limitingmembrane (arrow) which encloses granular and membranous contents. N, nucleus. (x27,000;inset, x855000.)

correspond to innumerable intracellularvacuoles with fibrillogranular and mem-branous lamellar contents.8 Furthermore,in MLS P9 and in various MPS's andSLS's,20 ultrastructural localization of acidphosphatase activity has been specificallyassociated with these storage vacuoles. Onthe basis of such histochemical and electronmicroscopic studies, therefore, it wouldappear that in the MLS's, as well as in theMPS's and SLS's, the storage vacuoles maybe derived from altered lysosomes whichhave become engorged with accumulatedAMP and glycolipid substances.

Among the clinical features of the pres-ent patient, symmetrically enlarged corneasand fine granularity of the corneal stromaare the only findings of direct ophthalmicinterest. Both megalocornea and buphthal-nios have been described in association

with the MPS's.21 In the absence of signsof increased intraocular pressure, therefore,the enlarged corneas of our patient may bea connective tissue abnormality which isrelated to defective AMP metabolism. Cor-neal clouding, which is associated withmany of the metabolic storage diseases,presumably results from the light-scatteringeffect of the abnormally accumulated stor-age substances which perturb the lamellarorganization of the corneal stroma (seeDiscussion, refs. 14 and 22). Accordingly,several ultrastructural studies of corneasaffected by various MPSV4> — and bygeneralized gangliosidosis10 have demon-strated excessive intracellular and extra-cellular AMP in quantities which corre-lated with the extent of corneal clouding.In MLS II, therefore, it is probable thatAMP and glycolipid deposits throughout


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Mucolvpiclosis II: I-cell disease 565

Fig. 10. The axonal process of a cutaneous nerve contains several membranous lamellar in-clusions (ML). A, axonal processes; S, Schwann cell cytoplasm. (x85,000.)

the cornea account for the fine stromalgranularity observable by slit lamp in thepresent patient.

It is of additional interest, however, thatin many of these storage disorders, cornealchanges seem to occur independently ofpathologic alterations in adjacent tissues.In particular, we have studied conjunctivalultrastructure in several of the MPS's andMLS's and have found that conjunctivalpathology is not always a reliable indicatorof corneal opacification. In the systemicMPS's, for example, although the degree ofvacuolation of conjunctival connective tis-sue cells paralleled the extent of cornealclouding in MPS types I, II, V, and VI,this relationship did not hold for MPS's IIIand IV.13 Moreover, in macular cornealdystrophy (an inherited localized disorderof AMP metabolism)23 and in Goldberg's

MLS variation,21 the cornea is clouded(presumably by AMP and glycolipid ac-cumulation) even though the conjunctivashows essentially no cellular defect. Andfinally, in comparing MLS II (I-cell dis-ease) and MLS III (pseudo-Hurler poly-dystrophy), we have determined thatthe ultrastructural alteration of the con-junctiva is far more severe in the formerdisorder, whereas corneal clouding is clini-cally significant only in the latter disease.The physicochemical basis for these specificreactions of the cornea to each disorder ofAMP-glycolipid metabolism remains to bedetermined.

The authors gratefully acknowledge Dr. John E.Dowling for use of laboratory facilities, Dr. RobertG. Wyllie for histochemical studies, Mr. KennethA. Linberg for technical assistance, Mr. TerryGeorge, R.B.P. for photomicrography, Mrs. Faye



Fig. 11. The peripheral cell (P) of a dermal capillary contains many vacuoles with granular,membranous, and electron-dense contents. The endothelial cells (E) lining the capillary areapparently unaffected. N, nucleus; asterisk, capillary lumen; BM, basement membrane.(xl3,300.)

Snyder for secretarial assistance, and Drs. W. R.Green, V. A. McKusick, H. A. Quigley, and C. I.Scott for critical review of the manuscript.

REFERENCES1. Spranger, J. W., and Wiedemann, H. R.: The

genetic mucolipidoses: Diagnosis and differ-ential diagnosis, Humangenetik. 9: 113, 1970.

2. Leroy, J. G., and DeMars, R. I.; Mutantenzymatic and cytological phenotypes in cul-tured human fibroblasts, Science 157: 804,1967.

3. Leroy, J. G., DeMars, R. I., and Opitz, J. M.:I-cell disease, in Clinical delineation of birthdefects, Vol. 6. IV. Skeletal dysplasias, Origi-nal Article Series, National Foundation—

March of Dimes, 1969, pp. 174-185.4. Matalon, R., Cifonelli, J. A., Zellweger, H.,

and Dorfman, A.: Lipid abnormalities in avariant of the Hurler syndrome, Proc. Nat.Acad. Sci. 59: 1097, 1968.

5. Leroy, J. G., and Spranger, J. W.: I-cell dis-ease (Cont.), N. Engl. J. Med. 283: 598,1970.

6. Luchsinger, U., Buhler, E. M., Menes, K.,and Hirt, H. R.: I-cell disease, N, Engl. J.Med. 282: 1374, 1970.

7. Lightbocly, J., Wiesmann, U., Hadorn, B., andHerschkowitz, N.: I-cell disease: Multiplelysosomal-enzyme defect, Lancet 1: 451,1971.

8. Kenyon, K. R., Wyllie, R. G.3 and Senseii-


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bienner, J. A.: Hepatic infrastructure andhistochemistry in mucolipidosis II (I-celldisease). In preparation.

9. O'Brien, J.: Generalized gangliosidosis, inClinical delineation of birth defects, Vol. 5.IV. Skeletal dysplasias, Original Article Series,National Foundation—March of Dimes, 1969,pp. 190-206.

10. Emery, J. M., Green, W. R., Wyllie, R. G.,and Howell, R. R.: Gin-gangliosidosis: Ocularand pathological manifestations, Arch. Oph-thalmol. 85: 177, 1971.

11. Scott, C. I.: Pseudo-Hurler poly dystrophy, inClinical delineation of birth defects, Vol. 6.VIII. The eye, Original Article Series, Na-tional Foundation—March of Dimes, 1971.

12. Quigley, H. A., and Goldberg, M. F.: Con-junctival ultrastructure in mucolipidosis III(pseudo-Hurler polydystrophy). In prepara-tion.

13. Kenyon, K. R., Quigley, H. A., Hussels, I.,Goldberg, M. F., and Wyllie, R. G.: Thesystemic mucopolysaccharidoses: Ultrastruc-tural and histochemical studies of conjunctivaand skin. In preparation.

14. Topping, T. M., Kenyon, K. R., Goldberg,M. F., and Maumenee, A. E.: Ultrastructuralocular pathology of Hunter's syndrome: Sys-temic mucopolysaccharidosis type II, Arch.Ophthalmol. In press.

15. Freitag, F., Kiichemann, K., Bliimcke, S., andSpranger, J.: Hepatic ultrastructure in fuco-

" sidosis, Virchows Arch. (Zellpathol.) 7: 99-113, 1971.

16. Freitag, F., Bliimcke, S., and Spranger, J.:Hepatic ultrastructure in mucolipidosis I(lipomucopolysaccharidosis), Virchows Arch.(Zellpathol.) 7: 189-204, 1971.

17. Loeb, H., Tondeur, M., Toppet, M., andCremer, W.: Clinical, biochemical and ultra-structural studies of an atypical form of muco-polysaccharidosis, Acta Paediatr. Scand. 58:220, 1969.

18. Van Hoof, F., and Hers, H. G.: L'ultrastruc-ture des cellules hepatiques dans la maladiede Hiirler (gargoylisme), C. R. Acad. Sci.Paris 259: 1281, 1964.

19. Freitag, F., Spranger, J., and Bliimcke, S.:Die Bildung von Speicherelementen in Leber-zellen bei Lipomucopolysaccharidose, Verh.Dtsch. Ges. Pathol. 54: 545-550, 1970.

20. Wallace, B. J., Volk, B. W., Schneck, L., andKaplan, H.: Fine structural localization of twohydrolytic enzymes in the cerebellum of chil-dren with lipidoses, J. Neuropathol. Exp.Neurol. 25: 76, 1966.

21. McKusick, V. A.: Heritable disorders of con-nective tissue, ed. 3, St. Louis, 1966, The C.V. Mosby Company, p. 335.

22. Kenyon, K. R., Topping, T. M., Green, W. R.,and Maumenee, A. E.: Ocular pathology ofthe Maroteaux-Lamy syndrome (systemicmucopolysaccharidosis type VI): A histologicand ultrastructural report of two cases, Am.J. Ophthalmol. In press.

23. Quigley, H. A., and Goldberg, M. F.: Scheiesyndrome and macular corneal dystrophy: Anultrastructural comparison of conjunctiva andskin, Arch. Ophthalmol. 85: 553-564, 1971.

24. Goldberg, M. F., Cotlier, E., Fichenscher, L.G., Kenyon, K. R., Enat, R., and Borowsky,S. A.: A new autosomal recessive storage dis-ease with macular cherry-red spot, comealclouding and beta-galactosidase deficiency:A clinical, biochemical and electron micro-scopic study. In preparation.


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Mucolipidosis II (I-Cell Disease): Ultrastructural Observations of