Neuropathology of Familial Erythrophagocytic Lymphohistiocytosis: Six Cases and Review of the Literature MICHIO AKIMA, MD, AND S. M. SUMI, MD The authors report the brain findings in six cases of familial erythrophagocytic lymphohistiocytosis (FEL) and review the literature, focusing primarily on the neurologic and neuropathologic aspects. Clinically, the most common neurologie abnormalities in the six patients were stupor or coma and seizures, with hemiplegia and cranial nerve palsies. Neuropathologic changes were characterized by infiltration of the meninges by lymphocytes and histiocytes and perivascular lymphocytic cuffing and diffuse proliferation of histiocytes in the brain parenchyma. The sevexity of the brain involvement was variable. In the mildest case there was only meningeal involvement. More severely involved cases showed meningeal and perivascular infiltration of lymphoid ceils in the brain. In the most severely involved cases, there was, in addition, diffuse cerebral infiltration by histiocytes accompanied by multifocal necrosis. Some cases showed disproportionately greater involvement of the brain than of the visceral organs. The authors conclude that "meningoencephalitis," histiocytic invasi:m, and necrotizing brain lesions are characteristic of FEL, although the m e c h a n i s m of their production is not known. Frequent seizures and disseminated intravascular coagulopathy may be contributory. HUM PATHOL 15:161--168, 1984. F a r q u h a r and Claireaux 1 first delineated a f o r m o f infantile recituloendotheliosis that is distinct f r o m Letterer-Siwe disease and is characterized by erythrophagocytosis, which they designated "familial hemoptmgocytic reticulosis." Since then, a n u m b e r o f similar cases have been r e p o r t e d u n d e r a variety o f diagnostic t e r m s , o f which the m o s t widely a c c e p t e d a p p e a r s to be "familial e r y t h r o p h a g o c y t i c l y m p h o histiocytosis," a term i n t r o d u c e d by MacMahon et al. 2 in 1963. T h e s e cases had a n u m b e r o f clinical and pathologic characteristics in c o m m o n , including infantile onset, familial o c c u r r e n c e , a n d r a p i d l y p r o g r e s s i v e febrile illness with anemia, pancytopenia, hepatosplenomegaly, and proliferation o f histiocytes containing e r y t h r o c y t e s . A l t h o u g h F a r q u h a r et al.1, 3 did n o t m e n t i o n any neurologic symptoms in their patients, s u b s e q u e n t authors2,4, 5 have n o t e d that n e u r o l o g i c a b n o r m a l i t i e s c o m m o n l y i n c l u d e a l t e r a t i o n o f the level o f consciousness, nuchal rigidity, seizures, and hemiparesis. However, most reports have m a d e only superficial r e f e r e n c e to the n e u r o l o g i c a n d n e u r o pathologic findings in these patients. Received October 25, 1982, from the Laboratory of Neuropathology, Department of Pathology, and Child Development and Mental Retardation Center, University of Washington School of Medicine, Seattle, Washington. Revision accepted for publication February 10, 1983. Dr. Akirna is currently at the Department of Pathology, Toho University School of Medicine, Tokyo, Japan. Address correspondence and reprint requests to Dr. Sumi: RJ05 Neuropathology, University of Washington School of Medicine, Seattle, WA 98195. V~re e x a m i n e d the brains o f six patients with tiffs disorder, five at autopsy and o n e by cortical biopsy, and reviewed the literature, focusing primarily on the neurologic and n e u r o p a t h o l o g i c findings. REPORT OF SlX CASES Tile pertinent findings are summarized in tables 1, 2 and 3. All the patients were admitted to Children's Orthopedic Hospital in Seattle, Washington. Case 1. A 6-month-old female infant, an only child, was admitted with fever, hepatosplenomegaly, and a petechial skin rash. Hetnoglobin was 28 per cent, and tile leukocyte count was 5,400/ram 3 with 65 per cent lymphocytes. Skeletal radiographs were normal. Cerebrospinal fluid (CSF) contained 73 erythrocytes/mm3 and nine leukocytes/ tnm+, with 120 mg/dl protein and 40 mg/dl glucose. Tile patient's course was complicated by disseminated intravascular coagulopathy. Site went into status epilepticus with conjugate gaze palsy to the left and a right facial pals)'. She died one and a half months after the onset of her illness. Autopsy revealed jaundice, diffuse macular cutaneous hemorrhages, and hepatosplenomegaly. All organs were infiltrated by lymphocytes and histiocytes, some of which had engulfed erythrocytes. The brain weighed 690 g after fixation. The leptomeninges were thickened and opaque over the cerebral convexities. Tile cerebrum was soft, and there were diffnse, symmetrical, indistinctly demarcated granular, necrotic areas throughout tile occipito-parieto-temporal gray and white matter, with smaller areas of necrosis in the basal ganglia (fig. 1). In addition, bilateral multifocal ttemorrhagic necrosis of the cerebellar white matter (fig. 2), inferior colliculi, and substantia nigra were present. There was diffuse infiltration of the meninges by lymphoid cells and histiocytes, some of which contained erythrocytes (fig. 3). The cerebrunt was diffusely infiltrated by fat-laden histiocytes and the normal architecture was destroyed. Histiocytic proliferation was more prontinent in the cortex, but the deeper structures appeared to be more edematous. In places, cortical necrosis had a laminar appearance. There was extensive perivascular lymphocytic infiltration. Erytttrophagocytosis was again easily identified. There was extensive necrosis and bistiocytic infiltration in the putamen, midbrain, and cerebellum with perivascular accumulation of iymphocytes. Case 2. A 4-month-old female infant was admitted one month before death, with fever, hepatosplenomegaly, anemia, and thrombocytopenia. An older sister had died at 3 months of age with an autopsy diagnosis of"atypical Letterer-Siwe disease." The patient's hematocrit was 33 per cent and the leukocyte count was 1,600/mm 3 with 90 per cent lymphocytes. Mild thrombocytopenia was present. Diagnosis of familial erythrophagocytic lymphohistiocytosis was made by liver biopsy. 161 HUMAN PATHOLOGY Volume f5. No. 2 [February '1984] TABLE t. Clinical and Laboratory Findings in Six Cases of Familial Erythrophagocytic Lymphohistiocytosis Age at Onset Familial (months), Sex Occurrence Duration of ilhtess (weeks) HepatosplenoLeukocytes/mm 3 ThromboFever megaly Anemia (% Lymph) cytopenia Case 1 511~, F No (only child) 6 + + + 4,800 (70) + Case 2 4, F Yes 2 + + + 1,600 (90) + Case 3 4112, F Yes 10 + + + Pancytopenia + Case 4 5, F Yes 20 + + + 15,300 (66) - Case 5 I I/2, ~| Yes 16 + + + 5,200 (63) + Case 6 I J/2, M Yes 1 + + + 6,100 (80) Subsequently, the patient developed otitis media and became lethargic. Left-sided seizures, which became generalized, followed. Left hemiparesis and multifocal seizure disorder continued, and the patient remained in coma. At autopsy there was generalized l y m p h a d e n o p a t h y and a moderate hepatosplenomegaly with infiltration of all o r g a n s by l y m p h o c y t e s a n d histiocytes, some o f which showed erythrophagocytosis. In addition, small infarctions were present in the spleen. T h e brain weighed 750 g a f f e r fixation and appeared normal externally, but on sectioning diffuse pseudolaminar necrosis o f the cerebral cortex was observed, which was most marked in the temporal lobes. There was a focal area o f softening in the right parietal lobe. Histologically, there was diffuse meningeal infiltration by lymphocytes and histiocytes. Erythrophagocytosis was noted. Shrunken, eosinophilic neurons with pyknotic nuclei were present in the cerebral cortex, and some regions showed extensive neuronal loss, pseudolaminar necrosis, and proliferation o f capillaries. Again, perivascular lymphocytic infiltration and large numbers o f foamy histiocytes were found in the cerebral white matter, basal ganglia, and thalamus (fig. 4). Similar changes were present in the cerebellum. Case 3. A female infant, one o f identical twins, was admitted at 41/2 months of age, with fever, hepatosplenomeg.aly, mild lymphadenopathy, anemia, and pancytopema. Cerebrospinal fluid findings were normal. Liver and lymph node biopsy findings were inconclusive. She was readmitted at 61/z months o f age with fever and increasing lethargy, followed by left- and right-sided focal seizures. Although the pupils were reactive to light, she would not follow light. T h e fundi were normal. She appeared to hear. T h e arms were held in flexion, and there was opisthotonus. At this time the CSF contained 3,000 erythrocytes, 20 neutrophils, and 60 monocytes per cubic millimeter, with 89 mg/dl protein and 51 mg/dl glucose. A ventriculogram showed slight ventricular dilation. Skeletal radiographs showed only slight widening o f the cranial sutures. T h e patient died 11 days after admission. General autopsy findings included an enlarged liver, spleen, and lymph nodes and infiltration by I)'mphocytes and macrophages with occasional erythrophagocytosis. T h e brain weighed 740 g after fixation. T h e brain was not swollen and showed only a small hematoma over the Biopsy Findings Bone marrow: erythroid hyperplasia and histiocytosis Bone marrow: normal; liver: lymphohistiocytic infiltration Bone marrow: reticuloendotheliosis; liver: nondiagnostic; lymph node: non-diagnostic Liver: lymphohistiocytic infiltration; lymph node: histiocytosis Bone marrow: non-diagnostic; lymph node: histiocytosis right frontal convexity at the site of the ventricular needling. Sections o f the cerebral hemispheres, cerebelhun, and brainstem showed no other gross abnormality. Microscopically, there was diffuse infiltration of the meninges by lymphocytes and large histiocytes, many o f which had engulfed tile erythrocytes in the hemorrhagic area. There was diffuse histiocytic and perivascular lymphocytic infiltration o f both the cerebral cortex and the white matter. T h e perivascular inflammation was so extensive that it resembled an encephalitic process (fig. 5). A mild proliferation of astrocytes was intermingled with the histiocytes. Striking perivascular lymphocytic infihration was also observed in the thalamus, globus pallidus, midbrain, and pons. In the cerebellum there was perivascular lymphocytic infiltration in the white matter, but the cortex was not involved, and similar, but milder, changes were found in the spinal cord. Definite areas of necrosis were not found. Case 4. T h e patient was the identical twin sister of the patient described in case 3. She was admitted at 5 months o f age with fever, hepatosplenomegaly, and anemia. T h e leukocyte count was 15,300/mm 3 with 34 per cent neutrophils, 52 per cent lymphocytes, and 14 per cent monocytes. Chest and skeletal radiographs were normal. T h e patient was readmitted at 8 months o f age, with fever and transient tremor o f the head and trunk, which was followed by stupor. Hepatosplenomegaly persisted, and she had nuchal rigidity. There was decreased muscle tone and bilateral Babinski signs. T h e CSF contained 27 mononuclear cells/mm 3 and 60 mg/dl protein. Splenectomy and liver and lymph node biopsies revealed infiltration by mononuclear cells in these organs, and a diagnosis o f reticuloendotheliosis was made. T h e patient had increasing numbers of generalized convulsions, and the course o f her illness was complicated by otitis media. She died two months after admission. At autopsy the liver was markedly enlarged with periportal infiltration by lymphoid cells and a few histiocytes. Similar changes were found in the kidneys and the lungs. Lymph nodes showed mild lymphocyte depletion and histiocytic proliferation. No erythrophagocytosis was seen. T h e brain weight was not available. T h e brain was very soft and friable, and the normal structures could not be identified. There was slight ventricular dilatation. Histologically, there was diffuse meningeal infiltration by lyre- 162 FAMILIALERYTHROPHAGOCYT1CLYMPHOHISTIOCYTOSIS[Akima & Sumi] TABLE 2. Neurological Findings, All Cases CSF Case No. Meningeal Signs Seizures Focal Signs Stupor/ Coma Leukocyteslmm s ('7,,, I)mphoc)tes) Protein (mg/dl) Glucose (mg/dl) Tiffs r e p o r t 1 2 3 4 5 6 + - + + + + + NA + + NA NA + NA + + + + + NA 9 (100) 7 (100) 80 (75) 27 (I00) 86 (72) 2 120 32 89 60 252 31 40 63 51 NA 37 30 Reese a n d Levy 8 1 2 NA NA + NA NA NA NA NA NA NA NA NA NA NA Farquhar and Claireauxl 1 NA NA NA NA NA NA NA Falk a n d Gellei 9 2 3 NA NA NA NA NA NA NA NA NA NA NA NA NA NA N e l s o n et al. 7 1 2 3 NA NA + + NA NA NA NA NA NA NA + 128 (100) 226 (99) 407 (96) NA 162 177 NA 38 16 Reference Farber a n d V a w t e r l0 NA + NA NA NA NA NA 2 + NA NA NA 63 (100) 476 64 Schoeck et al. II 1 NA NA NA NA NA NA NA Miller 13 L S V NA NA NA NA + NA NA NA NA NA NA NA NA N NA NA N NA NA N NA M a c M a h o n et al. 2 B e r a r d et al. 1~ 1 NCS NCS NCS NA N N N Bell et a l ) 4 I + NA NA + 16 (100) 50 N Buist et al. 16 1 2 NA + NA NA NA NA NA NA NA 40 (100) NA 35 NA NA Price et al. 6 1 2 3 NA NA NA + + + + - + + + 4 (100) 365 (I00) S 440 NA E NA NA E O ' B r i e n et al. 17 2 NA NA NA NA N N N Weinberg and R o g e r s 18 1 NA + NA + 8 (100) 10 63 NA NA NA + NA NA NA Koto et al. 4 A p p e n et al. 20 + + NA NA 56 (36) 160 42 Frisell et al. e2 1 2 NA NA NA NA NA NA NA NA NA NA NA NA NA NA A m b r n s o et al. ~3 1 NA + NA + NA NA NA NA + + + NA NA NA NA NA NA NA NA NA NA NA 150 (80)* NA NA NA NA NA Miller et al. 5 Lilleyman ~ 1 2 KEY: N A , n o t available; N, " n o r m a r ' ; NCS, " n o CNS signs"; S, "small n u m b e r " ; E, "elevated"; + , p r e s e n t ; - , absent. * Histiocytes, 19 p e r cent. phoid and histiocytic cells. The former were more abundant around blood vessels, and tile latter had engulfed erythrocytes and other cellular debris. There was extensive necrosis of the cerebrum so that the gray matter and white matter were indistinguishable. The molecular layer of the cortex was marked by proliferation of gemistocytic astrocytes, and the rest of the brain consisted of a loose accumulation of large foamy macrophages, wlfich showed active phagocytosis and marked perivascular infiltration by lymphoid cells with scattered islands of large astrocytes. normal architecture in the midbrain, pons, and medulla, with gliosis, perivascular lymphoid cell accumulation, and histiocytic proliferation. The spinal cord was better preserved and showed only perivascular lymphocytic infiltration. Case 5. T i l e p a t i e n t w a s t h e o l d e r b r o t h e r o f t h e t w i n s i s t e r s d e s c r i b e d in c a s e s 3 a n d 4. H e b e c a m e ill a t 6 w e e k s of age, with fever, hepatosplenomegaly, and anemia. The l e u k o c y t e c o u n t w a s 5 , 2 0 0 / m m 3, w i t h 6 3 p e r c e n t l y m p h o c y t e s . T h e p l a t e l e t c o u n t w a s 3 2 , 0 0 0 / m m 3. R e t i c u l o e n d o theliosis was diagnosed on lymph node biopsy. Fever rec u r r e d w h e n t h e p a t i e n t w a s 41/2 m o n t h s o f a g e , a n d h e The thalamus and basal ganglia were also necrotic and i n f i l t r a t e d b y m i c r o g l i a . T h e r e w a s e x t e n s i v e loss o f t h e 163 HUMAN PATHOLOGY Volume 15, No. 2 [February 1984] TABI.E :3. Neuropathological Findings, All Cases Gross Findings Meningeal Infiltration Perivascular Cuffing Cerebral Histiocytic Infiltration Necrosis 1 2 3 4 5 6 Necrosis Necrosis Small hematoma Necrosis (Biopsy only) Subaraclmoid hemorrhage +* +* +* +* No meninges +* +* + + +* + - +* + + + - + + + - Reese and LevyS 1 2 Peteclfiae Normal NA NA NA NA NA NA NA NA Farquhar and Claireauxl 1 Normal NA NA NA NA Falk and Gellei9 2 3 NA NA NA NA + + NA NA NA NA Nelson et al. 7 1 2 3 Petechiae NA Normal + + + + + + NA NA NA NA NA NA Normal + + NA NA Case No. This report Reference Farber and Vawteri0 MacMahon et al. -~ 2 Meningeal thickening +* + + NA Schoeck et al. n 1 NA + NA NA NA Mille#3 L S V NA NA NA + + + + + + NA NA NA NA NA NA Berard et al. 12 1 Normal . Bell et al. la 1 Reduced cortical thickness + + + - Buist et al. TM 1 2 Subdural hematoma NA + + NA NA NA NA NA NA Price et al.6 1 2 3 Necrosis Necrosis NA + +* + + +* + +* + +* + + - O'Brien et al. 17 2 NA NA + NA NA Weinberg and Rogers TM 1 Normal + + NA NA Koto et al. 4 Normal +* +* NA NA A p p e n et alY0 Meningeal hemorrhage along the brainstem +* +* NA NA . . . Frisell et al.2Z 1 2 NA NA NA NA + + NA NA NA NA Ambruso et al. 23 1 NA +* PML NA NA Wlfite matter necrosis +* +* + EMB NA (Biopsy only) + - + - NA NA NA NA Miller et al. 5 Lilleyman34 1 2 KEY: NA, not available; PML, "pathological features of progressive multifocal leukoenceplmlopathy"23; EMB, "extensive myelin breakdown"; + , present; - , absent. * With erythrophagocytosis. had twitching of tile left eyelid, face, arm, and leg. Tile CSF contained 11,400 erythrocytes, 63 mononuclear cells, and 23 neutrophils per cubic millimeter. Protein was 152 m g / d l , a n d glucose was 37 m g / d l . T h e p a t i e n t h a d f r e q u e n t left facial seizures, r i g h t facial w e a k n e s s , a n d h y p e r a c t i v e t e n d o n r e f l e x e s bilaterally. S u b d u r a l taps w e r e n e g a t i v e , b u t I0 d a y s l a t e r t h e y r e v e a l e d a l a r g e s u b d u r a l h e m a t o m a , w h i c h was r e m o v e d surgically. C e r e b r a l cortical b i o p s y was p e r f o r n t e d . T h e p a t i e n t c o n t i n u e d to h a v e spasticity a n d f r e q u e n t m u s c l e t w i t c h i n g , a n d h e d i e d a t h o m e at 51/o. m o n t h s o f age. A n a u t o p s y was n o t p e r f o r m e d . T h e b r a i n b i o p s y showed dense gliosis with perivascular cuffing of lymphocytes. Case 6. A 7 - w e e k - o l d m a l e i n f a n t was in g o o d h e a h h u n t i l f o u r days b e f o r e his d e a t h , w l t e n h e was a d m i t t e d with fever, hepatosplenomegaly, and anemia. Cerebrospinal fluid c o n t a i n e d 2 l y m p h o c y t e s / m m 3, with 70 m g / d l p r o t e i n a n d 52 m g / d l glucose. D e s p i t e a d m i n i s t r a t i o n o f antibiotics, steroids, a n d -/ g l o b u l i n , t h e p a t i e n t died. A n o l d e r sister with a s i m i l a r h i s t o r y h a d d i e d , b u t n o a u t o p s y h a d b e e n performed. General autopsy findings for the male infant included jaundice, ltepatosplenomegaly, and generalized iympltad- 164 FAMILIALERYTHROPHAGOCYTICLYMPHOHIS110CYTOSIS(Akima & Sumi] at least one other similarly affected sibling and consanguinity was not a factor. Similar familial involvem e n t was p r e s e n t in the m a j o r i t y o f the r e p o r t e d cases. T h e s e data s u p p o r t an autosomal recessive m o d e o f inheritance. In all o u r patients, the illness beg.an within the first six m o n t h s of life and the dur a n o n o f illness was brief, all patients s u c c u m b i n g within five months. T h e age distribution of o u r patients conforms to that reported by most authors. Exceptions were the family reported by Price et al., 6 in which the youngest affected child was 7 m o n t h s old and the others were 10 months, 18 months, and 6 years old at onset o f disease, and the families reported by Nelson et al., 7 two o f whose patients were 3 and 7 years old, respectively. We restricted o u r literature review to those reports in which reference was m a d e to the brain, either at autopsy or on biopsy. T h e r e were 31 cases in 20 reports that fulfilled this criterion,l,%4-14A6-1s,20,22 -24 but very few of these reports contained detailed clinical or pathologic descriptions o f the nervous system. T h e thoroughness with which the nervous system was evaluated varied greatly (tables 2 and 3), so it was impossible to determine the true incidence of neurologic involvement in this disease. T h e most c o m m o n brain abnormality was the nilcroscopic appearance of "leptomeningitis," consisting o f diffuse or patchy infiltration by lymphocytes and histiocytes. This was f o u n d in all o u r patients and in 21 of the 31 reported cases. Grossly visible leptomeningeal thickening was observed in only one of o u r cases (case 2) and in case 2 o f MacMahon et al., 2 and in neither was it striking. Erythrophagocytosis was present in the meninges in all five of our autopsied cases and in six reported cases (table 3). In contrast, nuchal rigidity was an u n u s u a l clinical finding, being FIGURE t (top). Case 1. Multiple foci of necrosis of the frontal, insular, and temporal cortexes and in the central white matter, pulamen, and palIidum. FIGURE 2 [Boflom]. Case 1. Multiple areas of hemorrhagic necrosis in the cerebellar white matter. enopathy, with infiltration by lymphoid cells and histiocytes that exhibited erythrophagocytosis. The brain weighed 580 g after fixation. There was a small amount of subaraclmoid blood in the rigbt precentral region. Bile-staining of the choroid plexus was the only other abnormality observed in the gross brain. Microscopically, there was lymphocytic and histiocytic infiltration of the leptomeninges (fig. 6), but no parenchymal involvement was seen. DISCUSSION All o u r patients had the clinical and pathologic features o f familial erythrophagocytic lymphohistiocytosis (FEL). Fever, h e p a t o s p l e n o m e g a l y , a n d anemia were c o m m o n to all, and lymphohistiocytosis with erythrophagocytosis was present in the viscera or the brain in all. F o u r o f o u r six patients were girls, and two were boys. In all but one (an only child, case 1), there was FIGURE 3. Case I. Infiltration of the pia mater by l~'nphoc~/tes and histioG~/tic cells containing e~hro~/~es [arrows] in case I. The subpial region shows proliferation of astroo~es and histioc,~ic infiltration. (Hematoxylin-eosin stain, x 400.) 165 HUMAN PATHOLOGY Volume 45. No. 2 (February 1984) ........... +;- 9 -- +. +~ 9 qlo% 9 - 9 4P9 ;, . ~ e ...... ~'. + +~, . , ..,. .~_ :..,.- .. ,,......~ ...., + -~-~.~,.~,~.~'~. .+% ~ "9 .- hid i ,~. . ,,, 9 ..'+~"~ 9 ~. ,~ V .." ............. . : , ~ . ... ~ ,,' + I + 9 9 9 " . ..~ .~, + , " ! + ,., .~ ... . al, , ~ , -k ',~9 ~, ",,~ 9 i ,Q . ~ , 9 ..... + .... tr Ja~ 9 r! ~ ' e q -9 I . ..,~.~,,.~; + 'iP', .~ ? " .+'~ , "P : ., ". . . . . . . : ?;O.++ .'+ . ~ , , + 011 " +!+. + . Ae -?,.'..+i +, +,;'t ,..++., +t,, , . . +e FIGURE 4 (top row). Case 2. Left, several foci of perivascular lymphocytic accumulation, and diffuse infiltration of adjacent brain tissue by macrophages. [Hematoxylin-eosin stain. x 100.) Right, one such focus at higher magnification, (Hematox-u stain, x 230.) FIGURE 5 (middle row). Case 3. Left, occipital lobe white matter with an "encephatitic" appearance due to extensive perivascular lymphocytic infiltration. (Hematoxylin-eosin stain. x40.] Right, high-power view showing details of infiltrating cells, lymphocytes, and foamy macrophages. [Hematoxylin-eosin stain. x 500.) FIGURE 6 (bottom). Case 6. Meningeal Infiltration by lymphocytes and histiocytes, cerebellum. [Hematoxytin-eosin stain, x 100.] 466 9 '~' .9149 FAMILIALERYIHROPFIAGOCYrlCLYMPHOHISTIOCYIOSIS[Akima & Sumi] present only in our case 4 and in five of the reported cases (table 2). Cerebrospinal fhfid abnormalities correlated much better and were a frequent finding. In all five of our cases in which the CSF was examined, there was mononuclear leukocytosis, elevation of protein, and depression of glucose content. Similar restilts were reported for 12 of the 15 published cases in which this examination was carried out (table 2). Ahhough the leukocytosis and increased protein content can be readily explained by the autopsy findings, the reason for the relative depression of glucose is not readily apparent. There was no evidence of bacterial or fungal infection in any of these cases. T h e hypoglycorrhaclfia may have been due to the rapid proliferation of histiocytes and lyutphocytes, to the phagocytic activity of the histiocytes, or to an alteration in the blood-CSF barrier to glucose, as has been suggested to explain the hypoglycorrhachia associated with meningeal cancer 25 and meningitis.26-29 Hemophagocytosis in the CSF was recorded in one patient by Hsu and Kontp 30 on cytopathologic examination, a technique that may provide further aid in establishing this diagnosis in fi~ture cases. Grossly, only a single focal h e m o r r h a g e was present in each of two cases--at the site of a frontal ventricular needling in case 1 and in the precentral region in case 6. No other macroscopic abnormality was observed in these cases. Subdural hematoma occurred in one patient (case 5) and in the first patient reported by Buist et al. 16 In our patient, a child with " thrombocytopenia, the hematoma was probably the result of the negative ventricular-tap performed 10 days previously. In addition to the infiltration of the leptomeninges, another constant microscopic finding was perivascular accumulation of lymphocytes and foamy histiocytes. This was present in all our cases and in 23 cases from the literature (table 3). There also was diffuse histiocytic infiltration of the brain parenchyma without evident necrosis in case 3, which was apparently found in three reported cases. In three of our cases and in four other reported cases, muhifocal or diffuse areas of necrosis were present, but in none of the cases was vascular occlusion demonstrated. T h e severity of the brain abnormalities appeared to be related, in part, to the duration of the illness. The nfildest involvement, consisting of only patchy meningeal infiltration, was observed in patient 6, who survived only one week, while the most severe changes were present in patients 1 and 4, who survived 20 and 6 weeks, respectively. Necrotic lesions were present also in three patients described by Price et al. 6 who survived five months, ten months, and six years, respectively; in that of Miller et al., 5 who survived two months; and in that of Ambruso et al., 23 who survived more than 13 weeks. In some pat i e n t s - o u r cases 1 and 4 and those of Price et al. 6-the brain abnormalities were much more extensive than those in the visceral organs. These patients had the longest survival times. In fact, the almost complete sparing of the viscera despite the extensive in- volvement of tile nervous system as well as the later onset of the illness in the patients reported by Price et al. raises the possibility that they suffered from a closely related but separate disease. However, until the pathogenesis of this disease is understood, it is impossible to determine whether this was the case. Two patients with apparent restriction of the necrosis to the cerebral white m a t t e r have been described. In one, Ambruso et al. 23 reported "pathological features of progressive multifocal leukoencephalopathy" without viral inclusions. In the other, Miller et al. 5 found "extensive myelin destruction" with sparing of the subcortical U fibers, in addition to the lymphocytic and histiocytic infiltration of the leptomeninges and the brain. Ahhough erythrophagocytosis was demonstrated in leptomeningeal histiocytes in all five of our cases examined at autopsy, this feature was observed in the cerebrum in only two (cases 1 and 4). Er),throphagocytosis was r e c o r d e d in only six r e p o r t e d c a s e s - four in the leptomeninges and two in the cerebrum (table 3). This may be a reflection of the care with which the brain was examined and the findings recorded. Peterson and Kuwabaral5 and Appen et al. 2~ described ocular lesions in two patients, consisting of swelling of the optic nerve head with infiltration by histiocytes and lymphocytes. T h e eyes were not studied in any of our cases. Patient 1 would not follow light, but the fundoscopic examination revealed no abnormalities. The surprising rarity of nuchal rigidity, with almost constant microscopic meningeal infiltration, has already been noted. In contrast, alterations in level of consciousness were very common findings, even in the absence of other neurologic abnormalities and may have been due in some patients to the metabolic changes induced by the multiple organ involvement. In others, such alterations may have resulted from cellular infiltration ("encephalitis") of the brainstem, and in others they may have been a consequence of convulsions. It seems unlikely that this was a reflection of increased intracranial pressure due to cerebral swelling or hydrocephalus, since these changes were conspicuous by their absence. Ahhough the pathogenesis of the CNS involvement in FEL has not been established, the disease is considered a non-neoplastic histiocytosis4 whose cause has not been identified. The leptomeningeal and perivascular infiltration by lymphocytes and histiocytes suggests an inflammatory process. As Hsu and Komp 3~ have noted, there has been frequent mention of "meningitis" in the older siblings of affected patients. However, no infectious agent has been identified. Although Ambruso et al. 23 thought that their findings suggested progressive muhifocal l e u k o e n c e p h a l o p a h t y (PML), no other r e p o r t e d cases, including ours, had such a distribution of lesions, and those investigators 23 did not find intranuclear inclusions in oligodendroglia or atypical astrocytes, the diagnostic features of PML. 31 Similarly, 167 HUMAN PATHOLOGY Volume 15, No. 2 [February 1984) perivenous demyelination suggesting post-infectious or para-infectious encephalomyelitis as reported by Miller et al. 5 appears to be a unique observation in FEL. Such an "allergic" inflammatory disease appears to be very rare in infants, de Vries 32 having reported that he was unable to find an)' instance of encephalomyelitis after vaccination in clfildren under 2 )'ears of age. Two reports have documented immunologic abnormalities in patients with FEL. Fullerton et al. 19 found nmrked deficiency in tire lymphocytic reaction to plwtohemagghttinin, decreased glucose oxidation by phagocytosing cells, and low IgA levels. Ladisch et al. 33 also found defects in both humoral and cellular immunity. Whether these immunologic deficiencies are the primary defects in FEL is not known. Previously, Miller 13 had suggested that FEL is a manifestation of a graft-versus-host reaction to maternal-to-fetal "transplant" of lympltocytes. However, the distribution of T and B cells is normal, 21 and maternal lymphocytes have not been demonstrated.19 Necrotic lesions in the brain may be due to multiple infarctions, but occluded blood vessels lmve not been described in an)' patient with FEL. Disseminated intravascular coagulation, which was observed in two of our patients (cases 1 and 2), is a recognized complication, 4,17 and small blood vessel occlusions could lead to multifocal seizure, coma, and focal neurologic findings. Such lesions could explain the histiocytic infiltration in areas of necrosis, but perivascular lymphocytic infiltration is never a prominent feature of cerebral infarction. In addition, there are cases with extensive histiocytic infiltration without necrosis. At this time, therefore, there is no obvious explanation for tire frequent occurrence of neurologic and neuropathologic abnormalities in FEL except as part of a generalized, multi-organ dissemination of disease. Acknowledgment. T h e a u t h o r s t h a n k the m e m b e r s o f the D e p a r t m e n t o f Pathology, C h i l d r e n ' s O r t h o p e d i c Hospital, Seattle, for m a k i n g t h e atttopsy and biopsy material a n d t h e i r reports freely available to us. REFERENCES 1. Farquhar JW, Claireaux AE: Familial haenmphagocytic reticulosis. Arch Dis Child 27:519, 1952 2. MacMahon tIE, Bedizel M, Ellis CA: Familial erythrophagocytic lymphohistiocytosis. Pediatrics 32:868, 1963 3. 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