KSHV Viral Load and Interleukin-6 in HIV-Associated Pediatric Kaposi Sarcoma—Exploring the Role of Lytic Activation in Driving the Unique Clinical Features Seen in Endemic Regions

Abstract

Kaposi sarcoma (KS) is among the most common childhood malignancies in central, eastern, and southern Africa. Although its unique clinical features have been established, biological mechanisms related to the causative agent, KS-associated herpesvirus (KSHV), have yet to be explored in children. We performed a prospective observational pilot study to explore associations between KSHV viral load (VL), human interleukin-6 (IL-6) and IL-10 levels, and clinical characteristics of 25 children with KS in Lilongwe, Malawi from June 2013-August 2015. The median age was 6.4 years. Lymphadenopathy was the most common site of KS involvement (64%), followed by skin and oral mucosa (44% each), woody edema (12%), and pulmonary (8%). Baseline samples for plasma KSHV VL, IL-6 and IL-10 analyses were available for 18/25 patients (72%) at time of KS diagnosis. KSHV VL was detectable at baseline in 12/18 (67%) patients, the median baseline IL-6 level was 8.53 pg/mL (range 4.31−28.33), and the median baseline IL-10 level was 19.53 pg/mL(range 6.91−419.69). Seven (39%) patients presented with an IL-6 level >10 pg/mL (exceeding twice the upper limit of normal). Detectable KSHV VL was significantly associated with lymphadenopathic KS (P=0.004), while having undetectable KSHV VL was associated with a higher likelihood of presenting with hyperpigmented skin lesions (P=0.01). Detectable KSHV VL and elevated IL-6 levels are present in a subset of children with KS. Lytic activation of KSHV and associated elevation in KSHV VL may contribute to the unique clinical manifestations of pediatric KS in KSHV-endemic regions of Africa.

INTRODUCTION

Whereas adult Kaposi sarcoma (KS) has been intensely studied since its classification as an AIDS defining malignancy, pediatric KS with or without HIV co-infection has been a neglected disease entity. Although contemporary descriptions of pediatric KS have shed light on the unique clinical features of disease in children, the virologic and biological underpinnings have yet to be explored in children.^1–7 Caused by KS-associated herpesvirus (KSHV), also known as human herpesvirus-8, KS is currently among the most common childhood malignancies in KSHV-endemic regions including central, eastern and southern Africa.⁸ While KS in children can manifest with prototypical hyperpigmented skin and oral lesions, woody edema, or visceral disease, clinical features unique to pediatric KS include lymph node involvement, even in the complete absence of skin/oral lesions, and severe cytopenias.^{1–5, 7} In KSHV-endemic regions of Africa, lymphadenopathic KS is the most common clinical phenotype, demonstrating features that overlap with KSHV-associated lymphoproliferative disorders such as multicentric Castleman disease (MCD) and KSHV inflammatory cytokine syndrome (KICS).^{5, 9, 10}

Based on the role of viral lytic activation in MCD and KICS,^{9, 11} we hypothesized that there may be overlap in mechanisms of KSHV-driven biology in children with lymphadenopathic KS. KSHV is known to encode viral interleukin (IL)-6, the homolog of human IL-6, and its expression is induced during viral activation and in response to inflammatory cytokines.^{12, 13} Adult KS in the United States and Europe—regions with low KSHV prevalence and ready access to antiretroviral therapy—generally occurs in the context of latent phase KSHV infection, and few if any tumor cells express viral lytic genes.^{11, 14} This is however, not the case in regions of endemic KS like Malawi, where approximately half of treatment-naïve KS lesions in adult HIV-infected KS patients show evidence of extensive lytic transcription.¹⁴ Features of KSHV lytic activation—including elevated KSHV viral load (VL) and IL-6 levels—are characteristic of KSHV-associated lymphoproliferative disorders such as MCD, KICS, and primary effusion lymphoma.^{9–12, 15–17}

Molecular profiling studies of KSHV transcription in adult KS patients in Malawi as well as the United States uncovered substantial heterogeneity.¹⁴ While the KSHV transcription profiles of patients in the United States displayed transcription limited to the latency locus in the majority of cases, analyses of Malawian adults demonstrated the existence of at least two subtypes of KS lesions, including a sub-group with a cluster of lesions that transcribed viral RNAs across the length of the KSHV viral genome.¹⁴ Consistent with increased KSHV transcription in the lesions, two studies evaluating KSHV VL in African adults with KS found relatively high frequency of KSHV viremia—66% in Zimbabwe and 82% in Central African Republic.^{18, 19} This contrasts with 39% of adult KS patients from the United Kingdom having detectable KSHV VL in plasma.²⁰

Acknowledging the prominence of lymphadenopathic KS in children living in KSHV-endemic regions of Africa, and the potentially distinct biological mechanisms of disease in this region, we sought to explore virologic characteristics of pediatric KS and potential clinical associations.

METHODS

We performed a prospective observational pilot study of the clinical and virologic characteristics of HIV-infected children and adolescents in Lilongwe, Malawi with newly diagnosed KS from June 2013-August 2015. Pathology-based diagnostic confirmation of KS was based on morphological findings of spindle cell infiltrates and positivity for the KSHV latency-associated nuclear antigen (LANA) on immunohistochemical staining. Clinical information was collected using standardized institutional clinical pathways that have been previously described.^{5, 6} All patients were treated with chemotherapy plus combination antiretroviral therapy according to Malawian national guidelines.^{5, 6} The AIDS Clinical Trial Group TIS staging criteria and Lilongwe Pediatric KS Staging Classification were applied based on established guidelines.^{6, 21, 22} The Lilongwe Pediatric KS Staging Classification stratifies four distinct clinical categories based on clinical presentation to address the spectrum of clinical phenotypes specifically seen in childhood KS in KSHV-endemic regions. Stage 1 represents children with disease limited to mild/moderate cutaneous/oral lesions, stage 2 includes those with lymphadenopathic KS, stage 3 represents patients with woody edema, and stage 4 consists of those with visceral and/or disseminated cutaneous/oral lesions.^{6, 22}

Plasma samples were collected at baseline and again while in a state of clinical remission and stored at −70°C. The samples were evaluated for KSHV VL, human IL-6 and IL-10 levels (elevated IL-10 is associated with MCD and KICS).⁹ Because other KSHV-associated malignancies (primary effusion lymphoma, plasmablastic lymphoma, and germinotropic lymphoproliferative disorder) are often co-infected with Epstein-Barr virus (EBV), we evaluated EBV VL concurrently. DNA was isolated using the MagnaPure Compact system (Roche Inc.) and the KSHV VL was determined in plasma by real-time quantitative polymerase chain reaction assay using the LANA78 primers (5’-GGAAGAGCCCATAATCTTGC and 5’-GCCTCATACGAACTCCAGGT) and ABI SYBR Select Mastermix (Thermo Fisher Scientific) as the method of detection.^{14, 23} IL-6 and IL-10 levels were quantified using commercial ELISA kits (eBioscience Ready-SET-GO). Generally, IL-6 and IL-10 levels greater than 5 pg/mL are considered above normal. EBV VL was measured simultaneously as previously described.²⁴

Standard descriptive statistics were used to report clinical and virologic data. Detectable KSHV VL levels were logarithmically categorized based on quantitative values of <1,000 copies (cp)/mL, between 1,000−10,000 cp/mL, and >10,000 cp/mL. Extrapolating from conventions used for defining extreme elevations of lactate dehydrogenase as a tumor biomarker for pediatric Burkitt lymphoma, extreme elevations of IL-6 were defined as exceeding twice the upper limit of normal, ie >10 pg/mL. For comparison of the virologic results across various clinical characteristics, KSHV VL was dichotomized as detectable versus undetectable (<50 cp/mL) and elevated IL-6 was defined as greater than the median of 8.5 pg/mL versus levels below this threshold. Differences in clinical characteristics between those with and without detectable KSHV VL, and with and without elevated IL-6 levels, were assessed using a k-sample equality-of-medians test with Fisher’s exact P-value reported or Fisher’s exact test, as appropriate. Given sample size considerations, we report Fisher’s exact P-values generated from each statistical test. No adjustments for multiple comparisons were made as multiple hypothesis testing was not conducted. All statistics are presented for descriptive purposes only. All analyses were conducted in STATA v.13.1. The Malawi National Health Sciences Research Committee plus the Baylor College of Medicine and University of North Carolina Institutional Review Boards for Human Subjects provided ethical approval. Guardians for all patients provided informed consent, while all children older than 5 years also provided assent. Consent and assent forms were translated into Chichewa, the national language of Malawi.

RESULTS

Clinical Characteristics

The clinical characteristics are listed in Table 1. A total of 25 HIV-infected patients (presumed perinatal transmission based on medical and social histories) were enrolled, 22 (88%) with biopsy confirmation. The most common clinical site of involvement was lymph node, followed by skin and oral lesions and woody edema. Nine patients (36%) presented primarily with lymphadenopathy in the absence of prototypical hyperpigemented skin/oral lesions or woody edema. Nearly half of the patients were on antiretroviral therapy at KS diagnosis and approximately one-fourth presented with severe suppression of the CD4 count at baseline. Based on the Lilongwe Pediatric KS Staging Classification, the majority of patients (52%) were categorized as stage 2 lymphadenopathic KS. Overall, 18 patients (72%) were alive with median follow-up time of 19.5 months (range 6−26); 17 were in complete remission (complete disappearance of all KS lesions).

Table 1:

Clinical Characteristics of the HIV-Related Pediatric Kaposi Sarcoma Cohort

Number of Patients	25
Gender, n (%)	Females 10 (40%)
Median Age (range)	6.4 years (1.7 - 17)
Pathology Confirmation, n (%)	22 (88%)
Anatomical Sites of KS Involvement, n (%)
Lymph Node	16 (64%)
Skin	11 (44%)
Oral	11 (44%)
Woody Edema	3 (12%)
Pulmonary	2 (8%)
ART Status at Time of KS Diagnosis, n (%)
Naïve to ART	12 (48%)
On ART	12 (48%)
Previously on ART but had defaulted	1 (4%)
ACTG T1 Stage, n (%)	5 (20%)
Lilongwe Pediatric KS Staging Classification, n (%)
Stage 1A, Mild Cutaneous/Oral KS	1 (4%)
Stage 1B, Moderate Cutaneous/Oral KS	4 (16%)
Stage 2, Lymphadenopathic KS	13 (52%)
Stage 3, Woody Edema KS	3 (12%)
Stage 4, Visceral and/or Disseminated Cutaneous/Oral KS	4 (16%)
Median CD4 Count (n=21), cells/mm3 (range)	515 (2 - 2,013)
Severe CD4 Count Suppression, n (%)	6 (29%)
Median HIV Viral Load (n=22), copies/mL (range)	97,000 (suppressed - 2.2 million)
HIV Viral Load Suppressed, n (%)	5 (23%)
Presence of Concurrent Opportunistic Illness, n (%)	2 (8%)
Hemoglobin < 8 and/or platelet count < 100, n (%)	8 (32%)
Median Platelet Count, cells x 10^9/L (range)	317 (7 - 729)
Median Hemoglobin, g/dL (range)	9.9 (4.8 - 12.5)

LEGEND: KS = Kaposi sarcoma, ART = antiretroviral therapy, ACTG = AIDS Clinical Trial Group

Virologic Characteristics

Baseline samples for plasma analyses were available for 18/25 patients (72%) at time of KS diagnosis (Table 2). KSHV VL was detectable in plasma at baseline in 12/18 (67%). Baseline KSHV VL measured 50−1,000 cp/mL in six patients, between 1,000−10,000 cp/mL in four, and two children had levels of 17,037 cp/mL and 656,164 cp/mL respectively. Median baseline IL-6 level was 8.53 pg/mL (range 4.31−28.33). At baseline, there were 7/18 patients (39%) with IL-6 levels >10 pg/mL (exceeding twice the upper limit of normal). The median baseline IL-10 level was 19.53 pg/mL (range 6.91−419.69). EBV was detectable in 6 patients (33%) at baseline with median level 8,745 cp/mL (range 1,786−94,950). Five (83%) of the EBV viremic patients presented with KS involvement of the lymph nodes.

Table 2:

Virologic Characteristics at Time of Kaposi Sarcoma Diagnosis

Variable		Baseline (n=18)
KSHV Viral Load Detectable, n (%)		12 (67%)
	> 10,000 copies/mL	2 (11%)
	1,000 – 10,000 copies/mL	4 (22%)
	50 – 1,000 copies/mL	6 (33%)
Median Human IL-6 Level, pg/mL (range)		8.53 (4.31-28.33)
Human IL-6 Level >10 pg/mL, n (%)		7 (39%)
Median Human IL-10 Level, pg/mL (range)		19.53 (6.91-419.69)
EBV Viral Load Detectable, n (%)		6 (33%)
Detectable EBV Viral Load Range, copies/mL		1,786-94,950

LEGEND: KSHV = Kaposi sarcoma-associated herpesvirus, EBV = Epstein-Barr virus

Follow-up samples were available for 10 patients in clinical remission at median time 6.5 months (range 4−8) after KS diagnosis. Eight (80%) had undetectable KSHV VL at the remission time point. Among the ten patients with follow-up data, five had previously demonstrated KSHV viremia at baseline. The KSHV VL in 3 patients went from detectable at baseline to undetectable in remission. Two patients demonstrated detectable KSHV VL in remission with VL levels of 639 cp/mL (decreased from baseline measurement of 4,068 cp/mL) and 4,698 cp/mL (increased from baseline measurement of 1,190 cp/mL) respectively.

Associations between Clinical and Virologic Characteristics

Table 3 lists a comparison of clinical associations with baseline KSHV viremia and elevated IL-6 levels >8.5 pg/mL. Among patients with detectable KSHV, 11/12 (92%) had KS lymphadenopathy and the median age was 4.3 years; for patients with undetectable KSHV, 1/6 (17%) had KS lymphadenopathy and the median age was 12.8 years (P=0.004 for comparison of KS lymphadenopathy, P=0.13 for comparison of age). For patients with elevated IL-6 levels, 8/9 (89%) had KS lymphadenopathy, compared to 4/9 (44%) without elevated IL-6 (P=0.13). The two patients presenting with woody edema had undetectable KSHV (P=0.10) and IL-6 levels <8.5 pg/mL (P=0.47). KS skin lesions were present in 6/6 (100%) patients with undetectable KSHV, while only 4/12 (33%) with KSHV viremia had skin involvement (P=0.01).

Table 3:

Comparison of Baseline KSHV Viral Load & Human Interleukin-6 Levels and Associated Clinical Characteristics

VARIABLE		KSHV VIRAL LOAD		P	INTERLEUKIN-6 LEVEL		P
		DETECTABLE	UNDETECTABLE		IL-6 >8.5pg/mL	IL-6 <8.5pg/mL
Number of Patients		12	6		9	9
Median Age, yearsa		4.3	12.8	0.13	7.3	5	0.13
Females, n (%)b		5 (42%)	3 (50%)	1.00	4 (44%)	4 (44%)	1.00
Site(s) of KS Involvement, n (%)
	Skin Lesionsb	4 (33%)	6 (100%)	0.01	4 (44%)	6 (67%)	0.64
	Lymphadenopathyb	11 (92%)	1 (17%)	0.004	8 (89%)	4 (44%)	0.13
	Oral Lesionsb	4 (33%)	4 (67%)	0.32	3 (33%)	5 (56%)	0.64
	Subcutaneous Nodulesb	6 (50%)	1 (17%)	0.32	3 (33%)	4 (44%)	1.00
	Woody Edemab	0	2 (33%)	0.10	0	2 (22%)	0.47
	Pulmonaryb	2 (17%)	0	0.53	1 (11%)	1 (11%)	1.00
	Lymph Node ONLYb	6 (50%)	0	0.05	4 (44%)	2 (22%)	0.62
	Inguinal Involvementb	11 (92%)	1 (17%)	0.004	7 (78%)	5 (56%)	0.62
ACTG TIS Staging, n (%)
	T1 Stageb	2 (17%)	2 (33%)	1.00	1 (11%)	3 (33%)	1.00
	I1 Stageb	1 (8%)	3 (50%)	0.06	2 (22%)	2 (22%)	1.00
	S1 Stageb	2 (17%)	0	0.53	1 (11%)	1 (11%)	1.00
Pediatric KS Staging, n (%)b
	Stage 1A/1B, Cutaneous/Oral KS	0	3 (50%)	0.001	1 (11%)	2 (22%)	0.51
	Stage 2, Lymphadenopathic KS	8 (67%)	1 (17%)		6 (67%)	3 (33%)
	Stage 3, Woody Edema KS	0	2 (33%)		0	2 (22%)
	Stage 4, Visceral or Disseminated KS	4 (33%)	0		2 (22%)	2 (22%)
Anemia (hemoglobin <8 g/dL), n (%)b		5 (42%)	0	0.11	2 (22%)	3 (33%)	1.00
Thrombocytopenia (platelets <50), n (%)b		4 (33%)	0	0.25	4 (44%)	0	0.08
Median CD4 Count, cells/m3a		602	107	0.28	365	602	1.00
Naïve to Antiretroviral Therapy, n (%)b		7 (58%)	1 (17%)	0.25	5 (56%)	3 (33%)	0.19
HIV Viral Load Suppressed, n (%)b		2 (17%)	2 (33%)	0.57	1 (11%)	3 (33%)	0.58
Median IL-6 Level, pg/mLa		10.81	7.70	0.62	n/a	n/a	n/a
IL-6 Level >8.5 pg/mL, n (%)b		7 (58%)	2 (33%)	0.62	n/a	n/a	n/a
KSHV Viral Load Detectable, n b		n/a	n/a	n/a	7 (78%)	5 (56%)	0.62
Median KSHV Viral Load, copies/mLa		n/a	n/a	n/a	775	68	0.35
EBV Viral Load Detectable, n (%)b		5 (42%)	1 (17%)	0.60	5 (56%)	1 (11%)	0.13
Median Interleukin-10 Level, pg/mLa		31.51	8.44	0.13	23.01	17.8	1.00
Interleukin-10 Level >20 pg/mL, n (%)b		8 (67%)	1 (17%)	0.05	5 (56%)	4 (44%)	1.00

LEGEND: KSHV = Kaposi sarcoma-associated herpesvirus, IL-6 = human interleukin-6, KS = Kaposi sarcoma, ACTG = AIDS Clinical Trial Group, EBV = Epstein-Barr virus.

^aFisher’s exact P-value estimated from the k-sample equality-of-medians test

^bP-value estimated using the Fisher’s exact test.

The four patients presenting with severe thrombocytopenia (all with baseline platelet count <50 × 10⁹/L) had a median KSHV VL of 11,703 cp/mL (range 775−656,164), a median IL-6 of 17.45 pg/mL (range 12.71−28.33), and a median hIL-10 of 32.2 pg/mL (range 16.77−419.69). These four patients also had detectable EBV with a median VL of 34,247 cp/mL (range 6,273−94,950). All four of these patients had lymphadenopathic KS, and except for the patient with KSHV VL of 775 copies/mL, would potentially fit the diagnostic criteria for KICS based upon the following findings: KS lymphadenopathy, thrombocytopenia, and KSHV VL >1,000 copies/mL.^{9, 10}

Using the Lilongwe Pediatric KS Staging Classification to probe KSHV VL and IL-6 associations with clinical characteristics, data showed the following: all evaluable patients with stage 1A/1B mild/moderate cutaneous/oral KS (n=3) and stage 3 woody edema KS (n=2) had undetectable KSHV VL. In contrast, 8/9 (88%) patients with stage 2 lymphadenopathic KS and 4/4 (100%) with stage 4 visceral and/or disseminated cutaneous/oral KS had detectable KSHV VL (P=0.001). A comparison of IL-6 levels and pediatric KS staging was not statistically significant. Comparisons of KSHV VL and IL-6 levels with T1 versus T0 KS staging, HIV viral load suppression, and median CD4 count did not yield any significant associations.

DISCUSSION

KS in endemic regions differs in many ways from HIV-related KS in the United States and Europe. In endemic regions, KSHV is acquired during childhood and KSHV seroconversion is almost complete by adolescence. By contrast, KSHV is most often acquired in adulthood in regions with low population prevalence. In endemic, high prevalence regions with high rates of HIV infection, KSHV is acquired before the immune system is fully developed and childhood infection may ultimately progress to oncologic complications such as KS. This study presents novel data exploring the biology of childhood KS in a KSHV-endemic region of Africa. These data suggest that KSHV plasma viremia and elevated IL-6 levels are present in a significant subset of pediatric KS patients and that these biomarkers may correlate with clinical disease presentation.

An important finding in these analyses is the association of KSHV viremia with KS lymphadenopathy. One of the unique and common clinical characteristics of pediatric KS is the predilection to present primarily with lymph node involvement.^1–7 In a region where lack of access to pathology resources is a major limitation, prototypical clinical presentations of KS (ie with hyperpigmented skin/oral lesions and/or woody edema) are often diagnosed clinically.^{2–5, 7} KS lymphadenopathy though, is virtually impossible to establish without access to pathology resources, and patients with lymphadenopathic KS are often misdiagnosed/missed diagnoses.⁵ The detriment of these resource limitations is especially significant considering that lymphadenopathic KS carries an excellent prognosis if treated promptly with chemotherapy.^{5, 6} Therefore, there is valuable potential for KSHV VL to serve as a non-invasive diagnostic biomarker for lymphadenopathic KS.

Clinical presentation with severe cytopenias is unique and relatively common in childhood KS.^4–7 Statistically significant associations between clinical presentation with severe thrombocytopenia and elevated KSHV VL and IL-6 levels were not demonstrated, potentially limited by the small sample size. However, it is worth noting that detectable KSHV VL and elevated IL-6 levels (all greater than 10 pg/mL) were observed in all four patients in the cohort that presented with severe thrombocytopenia, potentially providing another diagnostic opportunity. A major limitation in patients with severe thrombocytopenia in a region with limited access to platelet transfusions is the challenge of safely performing diagnostic tissue biopsies due to the risk of bleeding.

Elevations in KSHV VL and circulating levels of human and viral IL-6 have an established role in the biology of KSHV, particularly in MCD, KICS, and primary effusion lymphoma.^{9–13, 16, 17} We hypothesized that KSHV viremia and IL-6 may play a role in driving the clinical features of patients with lymphadenopathic KS and severe cytopenias.⁹ Both lymphadenopathy and cytopenias are clinical features described in MCD and KICS, and both disease processes are associated with significant KSHV viremia and elevated human and viral IL-6 levels.^{9, 10, 25} The findings of KSHV viremia in children with lymphadenopathic KS and the observation of elevated IL-6 levels in those with thrombocytopenia may imply a potential role of inflammation driven by KSHV replication in these patients. Three patients in this cohort would potentially fit the diagnostic criteria for KICS based upon the combination of KS lymphadenopathy, thrombocytopenia, and KSHV VL >1,000 copies/mL (although C-reactive protein testing was not performed). Anti-IL-6 therapeutics are currently approved for treatment in idiopathic MCD, while studies are ongoing to determine if this will be an effective approach for KSHV-MCD (NCT01441063).^{11, 26} Though cost is a major obstacle for use in low-income settings, discovery of targeted non-cytotoxic therapy would represent an exciting frontier for KSHV-associated malignancies in Africa.

The Lilongwe Pediatric KS Staging Classification attempts to stratify four distinct groups with different responses to therapy—mild/moderate cutaneous/oral disease (stage 1), lymphadenopathic KS (stage 2), woody edema (stage 3), and visceral and/or disseminated cutaneous/oral disease (stage 4).^{6, 22} While the limited numbers of patients broken down by stage preclude definitive conclusions regarding associations with KSHV VL, we observed a distinct pattern with all 12 of the patients with detectable KSHV VL categorized as Stages 2 or 4, and 5/6 patients with undetectable KSHV VL being categorized as Stages 1 or 3. Of note, associations between HIV viral load suppression and CD4 count were not observed, suggesting that the virologic effects of KSHV may not depend on the effects of HIV viremia and/or the level of CD4 suppression.

Limitations of this study include the limited sample size, as working with a pediatric population is inherently challenging and this is exacerbated in resource-limited settings. Hence, statistical power was limited to detect only the most robust associations and more advanced statistical comparisons were not feasible. Therefore these results are exploratory in nature and a larger study will be required to adequately test hypotheses. Also, the limited number of remission time point samples precluded a comprehensive pair-wise comparison of the trajectory between baseline and remission time point analyses. Studies in a larger cohort are needed to derive definitive conclusions regarding the prognostic value of measuring KSHV VL and IL-6 and evaluate them as markers of treatment response and predictors of relapse. This precedent has been established in MCD and may be able to guide decision-making algorithms for disease monitoring and therapeutic interventions.²⁵ Additionally, larger scale analyses are required to determine the significance of concurrent EBV viremia and observations of its occurrence in patients with lymphadenopathic KS and thrombocytopenia. And although the KS diagnosis was pathology confirmed in 88% of the cohort, three patients were diagnosed clinically. Ultimately, all three had convincing clinical diagnoses, corroborated by a combination of the original clinical findings, the response to treatment, and the KSHV VL (two patients had elevated KSHV VL at baseline, while the third had undetectable KSHV VL but presented with classical hyperpigmented skin lesions that completely resolved with chemotherapy).

In conclusion, KSHV viremia and elevated IL-6 levels were present in the majority of pediatric KS patients at baseline. KSHV viremia was associated with lymph node involvement in childhood KS and differentiated distinct clinical phenotypes of pediatric KS. Increased viral replication and the concurrent elevation of IL-6 may contribute to the unique clinical manifestations of pediatric KS in KSHV-endemic regions.

Abbreviations:

KS

Kaposi sarcoma

KSHV

Kaposi sarcoma herpesvirus

MCD

multicentric Castleman disease

KICS

KSHV inflammatory cytokine syndrome

IL

interleukin

VL

viral load

LANA

latency-associated nuclear antigen

EBV

Epstein-Barr virus

cp

copies