Latent Profile Analysis of Cognitive Performance and Depressive Symptoms Among People with HIV

Depression and cognitive impairment are prevalent conditions among people with HIV (PWH), likely attributable to shared causes and common risk factors. Identifying subtypes of PWH with similar patterns of neurocognitive impairment (NCI) and depressive symptoms may inform development of patient-centered interventions that target-specific profiles. This study aimed to (1) classify PWH based on patterns of domain-specific NCI and depression; and (2) determine the relationship between latent class membership and pertinent clinical characteristics. PWH (N = 580, 86.2% male, 57.1% non-Hispanic White, 69.2% unemployed) completed a comprehensive neuropsychological test battery assessing global and domain-specific cognition. Domain-specific NCI was classified as deficit score >0.5. Participants completed the Beck Depression Inventory-II (BDI-II), and domain-specific BDI-II scores reflecting cognitive, affective, and somatic symptoms were computed. Latent profile analysis (LPA) was used to determine latent subgroups of NCI and depression. The optimal LPA solution consisted of five classes: minimal NCI and minimal depression (Class 1), amnestic and minimal depression (Class 2), severe multi-domain NCI and moderate depression (somatic and affective; Class 3), mild NCI and mild depression (Class 4), and moderate multi-domain NCI and severe depression (Class 5). Despite similar levels of functional impairment, Class 5 had a significant psychiatric profile, whereas Class 3 had a complex medical profile (i.e., higher frailty index, higher medications, greater proportion of AIDS diagnosis). In contrast, Class 1 had the lowest medication use and frailty index, with similar HIV disease characteristics to Classes 3 and 5. Our results suggest there are multiple pathways to cognitive and functional impairment among PWH with co-occurring depression and cognitive impairment, and these groups may respond differently to interventions. Of note, our sample was majority non-Hispanic White and male, which is nonrepresentative of the US population of PWH. Future interventions should consider a more integrated, person-centered approach that addresses cognitive and emotional health to optimize health outcomes in PWH.

Neurocognitive Dysfunction With Neuronal Injury in People With HIV on Long-Duration Antiretroviral Therapy

BackgroundNeurologic outcomes in people with HIV (PWH) on long-duration antiretroviral therapy (ART) are not fully understood and the underlying pathophysiology is unclear. To address this, we established a cohort of such individuals and compared them to HIV-negative controls using a novel matching technique. Both groups underwent extensive cognitive testing, evaluation for psychiatric measures, and MRI and cerebrospinal fluid (CSF) analyses.MethodsParticipants underwent comprehensive neuropsychological (NP) testing and completed standardized questionnaires measuring depressive symptoms, perceptions of own functioning, and activities of daily living as part of an observational study. Brain MRI and lumbar puncture were optional. Coarsened Exact Matching (CEM) was used to reduce between-group differences in age and sex, and weighted linear/logistic regression models were used to assess the effect of HIV on outcomes.ResultsData were analyzed from 155 PWH on ART for at least 15 years and 100 HIV-negative controls. Compared to controls, PWH scored lower in the domains of attention/working memory (PWH Least Square Mean [LSM]=50.4 vs. controls LSM=53.1, p=0.008) and motor function (44.6 vs. 47.7, p=0.009), and a test of information processing speed (symbol search 30.3 vs. 32.2, p=0.003). They were more likely to self-report a higher number of cognitive difficulties in everyday life (p=0.011). PWH also reported more depressive symptoms, general anxiety, and use of psychiatric medications (all with p<0.05). PWH had reduced proportions of subcortical gray matter on MRI (β=-0.001, p<0.001) and CSF showed elevated levels of neurofilament-light chain (664 vs. 529 pg/mL, p=0.01) and TNF-α (0.229 vs. 0.156 ng/mL, p=0.0008).ConclusionsPWH, despite effective ART for over a decade, displayed neurocognitive deficits and mood abnormalities. MRI and CSF analyses revealed reduced brain volume and signs of ongoing neuronal injury and neuroinflammation. As the already large proportion of virologically controlled PWH continues to grow, longitudinal studies should be conducted to elucidate the implications of cognitive, psychiatric, MRI, and CSF abnormalities in this group.

High Psychosocial Burden Relates to Poorer Antiretroviral Treatment Adherence Among Black/African American People with HIV

Black/African American communities continue to be disproportionately impacted by HIV with Black people with HIV (PWH) exhibiting poorer outcomes along the HIV treatment cascade. Psychosocial burden may, in part, explain these health disparities among PWH. We implemented a culturally adapted intervention [individualized Texting for Adherence Building (iTAB)] to improve ART adherence among 89 Black PWH in San Diego, CA. We aimed to (1) characterize psychosocial risk factors (depression, negative life events, discrimination, medical mistrust) hypothesized to be barriers to HIV outcomes among Black PWH and (2) determine if these factors influence intervention engagement, HIV outcomes, and self-reported physical and mental health. We identified three levels of psychosocial burden (low, moderate, high) through hierarchical cluster analysis. Participants in the high burden cluster (n = 25) experienced the highest levels of depression, negative life events, and discrimination, in addition to the poorest intervention outcomes, HIV outcomes, and physical and mental health compared to low and moderate burden clusters. Participants in the low (n = 29) burden cluster had less medical mistrust than the moderate (n = 34) and high burden clusters, but low and moderate clusters did not differ on any outcomes. Overall, self-reported ART adherence was 83%, which is above estimates of ART adherence in the Western region of the United States. The iTAB intervention shows promise in improving HIV-related outcomes among Black PWH with low to moderate psychosocial burden; however, additional supports may need to be identified for those with high psychosocial burden.

Four-Year Trajectories of Internal Strengths and Socioemotional Support Among Middle-Aged and Older Adults with HIV

Positive psychological attributes are associated with better health outcomes, yet few studies have identified their underlying constructs and none have examined their temporal trajectories in clinical vs. non-clinical samples. From data collected over 4 years from people with HIV (PWH) and HIV-uninfected (HIV-) participants, we identified two latent factors (internal strengths; socioemotional support) based on responses to seven positive psychological attributes. Internal strengths increased over 4 years for PWH, but not for HIV- comparisons. Socioemotional support did not change significantly in either group. Lower internal strengths and worse socioemotional support were related to greater depressive symptoms. We speculate that improvement in internal strengths in PWH could reflect their being in care, but this requires further study to include PWH not in care. Given the apparent malleability of internal strengths and their association with improved health outcomes, these attributes can serve as promising intervention targets for PWH.

Association of White Matter Hyperintensities With HIV Status and Vascular Risk Factors

OBJECTIVE

To test the hypothesis that brain white matter hyperintensities (WMH) are more common in people living with HIV (PLWH), even in the setting of well-controlled infection, and to identify clinical measures that correlate with these abnormalities.

METHODS

Research brain MRI scans, acquired within longitudinal studies evaluating neurocognitive outcomes, were reviewed to determine WMH load using the Fazekas visual rating scale in PLWH with well-controlled infection (antiretroviral therapy for at least 1 year and plasma viral load <200 copies/mL) and in sociodemographically matched controls without HIV (CWOH). The primary outcome measure of this cross-sectional analysis was increased WMH load, determined by total Fazekas score ≥2. Multiple logistic regression analysis was performed to evaluate the effect of HIV serostatus on WMH load and to identify MRI, CSF, and clinical variables that associate with WMH in the PLWH group.

RESULTS

The study included 203 PLWH and 58 CWOH who completed a brain MRI scan between April 2014 and March 2019. The multiple logistic regression analysis, with age and history of tobacco use as covariates, showed that the adjusted odds ratio of the PLWH group for increased WMH load is 3.7 (95% confidence interval 1.8-7.5; p = 0.0004). For the PLWH group, increased WMH load was associated with older age, male sex, tobacco use, hypertension, and hepatitis C virus coinfection, and also with the presence of measurable tumor necrosis factor α in CSF.

CONCLUSION

Our results suggest that HIV serostatus affects the extent of brain WMH. This effect is mainly associated with aging and modifiable comorbidities.

1176. Quality of Life of Previously Healthy Subjects following Cryptococcal Meningoencephalitis

Background

Cryptococcal meningoencephalitis (CM) causes significant morbidity and mortality in HIV-negative, previously healthy populations. This group has significant disease sequalae including a fronto-subcortical syndrome, hearing loss, vision loss, and spinal arachnoiditis. However, the health-related quality of life (HRQOL) of this group of patients following microbial recovery from infection has not been reported.

Methods

We cross-sectionally defined the HRQOL of previously healthy individuals with CM seen at the NIH Clinical Center since 2013 and at least one year past diagnosis using the Quality of Life in Neurological Disorders (Neuro-QoL) project short forms. These forms assess domains such as anxiety, fatigue, depression, dexterity and mobility in patients with chronic neurological disease. Form scores were calculated for each domain and centered to a general or clinical United States population reference. Impairment was considered a subject score of least one half a standard deviation (SD) lower than the population reference average.

Results

Of 43 subjects with CM (mean age 48 years, 56% male, mean time from diagnosis 5.7 years), 91% had evidence of impairment in at least one HRQOL domain. Notable findings included self-reported impaired cognitive function in 53% and sleep disturbance in 56%. Impaired satisfaction with social roles and activities was present in 44%. Mobility and dexterity were impaired in 30% respectively. The number of impaired HRQOL domains was not significantly different in subjects with a history of neurosurgical intervention during hospitalization (mean no. impaired domains 4.4 vs. 3.3, P=0.43) or methylprednisolone treatment for post-infectious inflammatory response syndrome (4.3 vs. 3.4, P=0.63). Cerebrospinal fluid glucose levels on admission were negatively correlated with the number of impaired functional domains (r_s=-0.33, P=0.05, n=38).

Patient reported quality of life domains following microbial recovery from cryptococcal meningoencephalitis. Box plots show median, 25th, and 75th percentiles.The gray dotted line represents the mean T-score (50) of the U.S. population reference for each Neuro-QoL domain. The yellow region designates mild symptoms or impairment (0.5-1.0 std below the population mean), orange, moderate (1.0-2.0), and red, severe (2.0-3.0). The asterisk* indicates measures that were centered to U.S. clinical reference population. All other domains were centered to a U.S. general population reference. Abbreviations: CNS, central nervous system, U.S., United States, ADL, activities of daily living, SRA, social roles and activities

Conclusion

This is the first report of HRQOL deficits in previously healthy individuals following microbial recovery from CM. These data reinforce and quantify the long-term morbidity of this disease and identify patient-centered outcomes for future interventional trials.

Disclosures

All Authors: No reported disclosures

Medical Symptom Validity Test (MSVT) profiles in individuals being evaluated for Alzheimer's disease

OBJECTIVE

Our purpose was to determine whether Medical Symptom Validity Test (MSVT) profiles could differentiate performance invalidity from true impairment in patients with varying levels of memory impairment and functional ability being evaluated for Alzheimer's disease (AD). Method: Seventy-three older adults (13 healthy controls, 25 mild cognitive impairment [MCI], 16 mild AD, 19 moderate AD) were evaluated with a neuropsychological battery including the MSVT and activities of daily living (ADL) measures. Using MSVT classification guidelines, examinees' MSVT profiles were categorized as: 1) valid, 2) invalid, 3) weak memory, or 4) genuine memory impairment (GMIP). Results: Eighty-four percent of moderate AD examinees produced a GMIP. Among MCI and mild AD examinees, who had only modestly affected ADLs, a substantial proportion manifested a GMIP (40% and 62.5%, respectively). An invalid profile was uncommon across patient groups (12.5% in mild AD, 5.3% in moderate AD, and 0% in MCI). Conclusions: The MSVT functions reasonably well in a dementia sample to determine if an examinee has an invalid profile, although for mild AD examinees, the false positive rate is slightly above the recommended 10% cut-off. However, even individuals with MCI, mild AD and relative preservation of ADLs may manifest a GMIP, demonstrating that such profile is found across patients with lower and higher degrees of functional impairment. Given this finding, the usefulness of the GMIP in differentiating performance invalidity from true impairment in patients being evaluated for AD appears limited.

When and how did you go wrong? Characterizing mild functional difficulties in older adults during an everyday task

Mild functional difficulties associated with cognitive aging may be reliably measured by coding "micro-errors" during everyday tasks, like meal preparation. Micro-errors made by 25 older adult and 48 younger adults were coded on four dimensions to evaluate the influence of: 1) poor error monitoring; 2) goal decay; 3) competition for response selection when switching to a new subtask; and 4) interference from distractor objects. Micro-errors made by young adults under a dual task load also were analyzed to determine the influence of overall performance level. Older adults' micro-errors were observed when switching to a new subtask and to unrelated distractors. Slowed error monitoring and goal decay also influenced micro-errors in older adults, but not significantly more so than younger adults under the dual task. Interventions to reduce interference from distractors and to increase attention at critical choice points during tasks may optimize everyday functioning and preclude decline in older adults.

HIV-Negative Cryptococcal Meningoencephalitis Results in a Persistent Frontal-Subcortical Syndrome

Twenty-seven previously healthy (of 36 consecutive eligible patients), HIV-negative cryptococcal meningoencephalitis (CM) patients underwent comprehensive neuropsychological evaluation during the late post-treatment period (1.3-4 years post diagnosis), assessing attention, language, learning, memory, visuospatial, executive function, information processing, psychomotor functioning, as well as mood symptoms. Seven of eight domains (all except attention) showed increased percentages of CM patients scoring in the less than 16^th percentile range compared to standardized normative test averages, adjusted for education level and age. Comparison with a matched archival dataset of mild cognitive impairment/Alzheimer's disease patients showed that CM patients exhibited relative deficits in psychomotor and executive function with fewer deficits in memory and learning, consistent with a frontal-subcortical syndrome. MRI evaluation at the time of testing demonstrated an association of lower neuropsychological functioning with ventriculomegaly. These studies suggest that CM should be included in the list of treatable causes of dementia in neurological work ups. Future studies are needed to identify diagnostic and treatment regimens that may enhance neurological function after therapy.

The neuropsychological phenotype of Chediak-Higashi disease

Background/objectives

Chediak-Higashi Disease (CHD) is a rare autosomal disorder, purported to have cognitive and neurological impairments. Prior descriptions of cognitive impairment, however, are solely based on subjective, unstructured observations rather than on formal neuropsychological measures.

Methods

Four pediatric and 14 adult patients with diagnostically confirmed CHD were administered a neuropsychological battery assessing memory, attention, processing speed, psychomotor speed, language fluency, executive function, and general intelligence. Nine of the adult patients received follow-up evaluations to elucidate the longitudinal progression or stability of cognition over time.

Results

Pediatric CHD patients performed within the average range. Adult patients, however, performed below average on nearly all measures administered, and endorsed subjective reports of learning difficulties and poor academic performance in childhood. In particular, patients struggled with memory and psychomotor speed tasks, with 75% or more of patients scoring in the bottom 2.3 percentile in these two domains. No significant declines in cognition were observed among the patients who completed follow-up evaluations (M = 39.90, SD = 8.03 months between visits). Exploratory analyses suggested that adult patients who had classic CHD and previously received bone marrow transplants (BMTs; n = 3) exhibited moderately greater cognitive impairment than adult patients who had atypical CHD and had not received BMTs (n = 10).

Conclusions

Adult patients with CHD uniformly exhibit deficits in multiple domains, but in psychomotor speed and memory, in particular. Based on their neuropsychological profile, their ability to hold jobs and succeed in school may require support and special accommodations. The source of cognitive deficits is probably multifactorial including central nervous system involvement in CHD, and, for those transplanted, BMT-related side effects and complications. Absence of cognitive decline at three-year follow-up is encouraging but does not exclude progression at a slower time-scale. Future work should elucidate the possible effects and timing of BMT on cognition, as well as the mechanisms driving neuropsychological impairment in CHD.

[Visual acuity and endothelial cell density following Descemet membrane endothelial keratoplasty (DMEK)]

PURPOSE

To assess the clinical outcomes of DMEK in the first series of 120 eyes operated for the treatment of Fuchs endothelial dystrophy in terms of visual acuity and endothelial cell density.

METHODS

The first 120 consecutive eyes that underwent DMEK (i.e. transplantation of an isolated donor Descemet membrane with its endothelium) were evaluated. In all eyes, the best corrected visual acuity (BCVA) before and at 1, 3 and 6 months after surgery, as well as the endothelial cell density (ECD) before and at 6 months were measured.

RESULTS

In eyes with a functional DMEK graft and good visual potential (n=96), the BCVA was ≥ 20/40 (≥ 0.5) in 77% after 1 month, 92% after 3 months, and 95% after six months; ≥ 20/25 (≥ 0.8) in 50%, 63%, and 73% of the cases, and ≥ 20/20 (≥ 1.0) in 23%, 34%, and 45% of the cases at 1, 3, and 6 months respectively. In this group, ECD averaged 2610 (± 185) cells/mm(2) before, and 1770 (± 520) cells/mm(2) at six months after surgery (n=96). In 15 eyes, a secondary Descemet stripping endothelial keratoplasty (DSEK) was performed. In this group, 91% of patients reached a BCVA of ≥ 20/40 (≥ 0.5) and only one patient achieved a BCVA of 0.8 at 6 months after surgery (n=11). Furthermore, ECD averaged 2580 (± 185) cells/mm(2) before and 1310 (± 740) cells/mm(2) at six months (n=13).

CONCLUSION

DMEK provides a fast and high visual rehabilitation. Endothelial cell density loss may be similar to earlier types of endothelial keratoplasty.

[Descemet membrane endothelial keratoplasty (DMEK): two-year results]

PURPOSE

To report the two-year results of Descemet membrane endothelial keratoplasty (DMEK) for managing corneal endothelial disorders.

METHODS

Non-randomized prospective clinical trial. A DMEK was performed in ten patients with Fuchs' endothelial dystrophy or bullous keratopathy. A 3.5 mm clear corneal incision was made and "under air" DM was stripped off from the posterior stroma. A 9.0 mm diameter, organ cultured donor DM roll was inserted into a recipient anterior chamber, positioned into the posterior stroma and secured by completely filling the anterior chamber with air for 30 minutes.

RESULTS

Three eyes showed complete detachment of the tissue; this was managed by a secondary Descemet stripping endothelial keratoplasty procedure. The remaining seven eyes had a best corrected visual acuity of >or=0.7 in three eyes (43%) at one month, in five eyes (71%) at six months, and in six eyes (86%) at one and two years. At six months, the endothelial cell density averaged 2039 (+/-373) cells/mm2 (n=7), at one year 1925 (+/-267) cells/mm2 (n=7) and at two years 1730 (+/-400) cells/mm2 (n=6).

CONCLUSIONS

DMEK may provide quick and nearly complete visual rehabilitation. Since the donor tissue can be stripped from donor corneo-scleral rims, the procedure may be readily accessible to most corneal surgeons.

Transient marked atelectasis: an unusual complication of asthma in pregnancy

We present an unusual case in which a patient with asthma presented with acute respiratory distress of acute onset, secondary to marked atelectasis of the right middle and lower lobes, which resolved within 24 hr following administration of increased doses of intravenous steroids, inhalation therapy (beta-agonists and steroids), and pulmonary physiotherapy. This transient occurrence responding to basic therapeutic measures was considered consistent with the release of a mucous plug which had caused the above obstruction and associated symptomatology and radiographic findings. This case illustrates and supports the practice of chest imaging in patients with atypical presentations of asthma and stresses the importance of pulmonary physiotherapy and bronchodilatory therapy as primary therapeutic agents in cases of mucous plug-associated atelectasis.

Induction of tyrosine hydroxylase by cyclic AMP and glucocorticoids in a rat pheochromocytoma cell line: effect of the inducing agents alone or in combination on the enzyme levels and rate of synthesis of tyrosine hydroxylase

The enzymatic activity of tyrosine hydroxylase (EC 1.14.16.2) increases in rat pheochromocytoma PC18 cells exposed to either elevated levels of cyclic AMP or glucocorticoids. The cyclic AMP-mediated increase in activity is elicited by cyclic AMP analogs or by compounds which activate adenylate cyclase or inhibit phosphodiesterase. The glucocorticoid-mediated increase is elicited only by glucocorticoid steroid hormones; nonglucocorticoid steroid hormones have no effect on tyrosine hydroxylase. In PC18 cells exposed simultaneously to both cyclic AMP-elevating agents and glucocorticoids, the increase in tyrosine hydroxylase activity is greater than that observed in cells treated with optimal concentrations of either inducing agent alone. Immunochemical titration experiments demonstrate that the increases in tyrosine hydroxylase activity observed in cells treated with the cyclic AMP analog, 8-bromocyclic AMP, and/or the synthetic glucocorticoid, dexamethasone, are due to increases in enzyme protein. Time course studies show that in cells treated with either 8-bromocyclic AMP or dexamethasone, the enzyme level increases slowly to a level 5-7-fold greater than that observed in untreated cells after 4 days of treatment. In cells treated with both of these inducing agents simultaneously, the enzyme level increases to a level 10-12-fold greater than that observed in control cells after 4 days of treatment. This additive increase in activity in cells treated with both inducing agents is observed at all time points. The rates of synthesis and degradation of tyrosine hydroxylase have also been measured in PC18 cells, using an antiserum to tyrosine hydroxylase to rapidly isolate radiolabeled enzyme from cells that have been incubated in the presence of [3H]leucine. The apparent half-life of tyrosine hydroxylase in the PC18 cells is approximately 30 hr. In PC18 cells incubated in the presence of radiolabeled leucine for 60 min, 0.2-0.3% of the total soluble protein synthesized is identified as tyrosine hydroxylase. In cells treated with either 8-bromocyclic AMP or dexamethasone for 24 hr, there is a 6-8-fold increase in the rate of synthesis of the enzyme. In cells treated with both inducing agents simultaneously, there is a 10-12-fold increase in the rate of synthesis; thus, the additive increase in enzyme level observed in cells treated with both inducing agents is paralleled by an additive increase in the rate of synthesis of the enzyme in these cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of mRNA for tyrosine hydroxylase by cyclic AMP and glucocorticoids in a rat pheochromocytoma cell line: evidence for the regulation of tyrosine hydroxylase synthesis by multiple mechanisms in cells exposed to elevated levels of both inducing agents

When rat pheochromocytoma PC18 cells are exposed to the cyclic AMP analog, 8-bromocyclic AMP, and/or the synthetic glucocorticoid, dexamethasone, there is a marked increase in the level of a single RNA species that hybridizes to the recombinant plasmid pTH.4, which contains sequences complementary to the RNA coding for tyrosine hydroxylase. This RNA species is 1800-1900 nucleotides in length and is presumably identical to an RNA species of similar size, isolated from rat pheochromocytoma PC8b cells and shown to code for tyrosine hydroxylase. Using RNA dot hybridization to quantitate the relative level of this tyrosine mRNA species, time course studies show that this mRNA increases relatively rapidly in PC18 cells treated with either 8-bromocyclic AMP or dexamethasone. A new steady state level of tyrosine hydroxylase mRNA is achieved after 6 hr or 12-24 hr of treatment with either 8-bromocyclic AMP or dexamethasone, respectively. The changes in the level of the mRNA slightly precede the changes in the rate of synthesis of tyrosine hydroxylase in cells treated with these inducing agents. After 24 hr of treatment with either 8-bromocyclic AMP or dexamethasone, the increases in the level of tyrosine hydroxylase mRNA are identical to the increases in the rate of synthesis of the enzyme in the cells. In cells treated simultaneously with both 8-bromocyclic AMP and dexamethasone, the increases in the enzyme level and rate of synthesis of tyrosine hydroxylase are approximately equal to the sum of the increases in these parameters observed in cells treated with either inducing agent alone. In contrast, there is not an additive increase in the level of tyrosine hydroxylase mRNA in cells treated with both inducing agents. This lack of an additive increase in mRNA for tyrosine hydroxylase is observed in total cellular RNA samples or in cytoplasmic RNA samples. Our results suggest that in cells exposed to elevated levels of either cyclic AMP or glucocorticoids, tyrosine hydroxylase is induced by a mechanism which increases the level of its mRNA, resulting in an increased rate of synthesis of the enzyme. However, in cells exposed to elevated levels of both cyclic AMP and dexamethasone, tyrosine hydroxylase enzyme levels are regulated by multiple mechanisms, one of which regulates the rate of synthesis of the enzyme without affecting the level of its mRNA.

Correction of feline arylsulphatase B deficiency (mucopolysaccharidosis VI) by bone marrow transplantation

Feline and human mucopolysaccharidosis VI (MPS VI or Maroteaux-Lamy syndrome) are inherited autosomal recessive deficiencies of lysosomal enzyme arylsulphatase B. Affected cats and children exhibit lesions caused by incompetent degradation, retinal atrophy and excessive urinary excretion of dermatan facial dysmorphia, corneal stromal opacities, leukocyte granulation, retinal atrophy and excessive urinary excretion of dermatan sulphate--and usually die before adulthood. Most attempts to treat humans affected with MPS VI or other mucopolysaccharidoses have been ineffective or logistically prohibitive, but allogeneic bone marrow transplantation (BMT) offers promise for cure of certain inborn errors of metabolism. Engraftment of normal donor marrow may endow the enzyme-deficient recipient with a continuous source of enzyme-competent blood cells and tissue macrophages to facilitate degradation of stored substrate and to prevent genesis of further malformations. To test this hypothesis, we performed allogeneic BMT in a 2-year-old male Siamese cat with advanced MPS VI. Here we describe BMT-induced correction of this hereditary enzyme deficiency.