Keywords
case report - AML - Klinefelter syndrome - FISH - conventional cytogenetics
Overview of KS and Its Clinical Features
Overview of KS and Its Clinical Features
Klinefelter syndrome (KS) is the most common sex chromosome aneuploidy in males and is typically characterized
cytogenetically by the presence of an extra X chromosome, most frequently resulting
in a 47,XXY karyotype. Clinically, individuals with KS often present with tall stature,
small firm testes, hyper gonadotropic hypogonadism, gynecomastia, infertility due
to azoospermia, and reduced secondary sexual characteristics.[1] Neurodevelopmental difficulties such as language delays, dyslexia, and executive
dysfunction are also commonly reported, contributing to social and academic challenges.[2] Despite an estimated incidence of 1 in 500 to 1,000 live male births, KS remains
significantly underdiagnosed, with only about 25 to 30% of affected individuals ever
being clinically identified. The diagnosis is frequently delayed or made incidentally
during evaluation for infertility or hematologic disorders.[3]
Beyond the classic features, KS is associated with a range of systemic complications.
Studies over the past decade have expanded the clinical spectrum to include increased
risk for metabolic syndrome, type 2 diabetes, osteoporosis, autoimmune diseases, and
thromboembolic events.[4] In addition, there is a recognized predisposition to malignancies, particularly
breast cancer and germ cell tumors (GCTs), attributed to the hormonal and chromosomal
alterations in KS.[5] Although hematologic malignancies are relatively rare in these patients, a growing
number of case reports have described associations between KS and both myeloid and
lymphoid leukemia.[6]
KS and Malignancy Risk
Men with KS, a chromosomal disorder characterized by a 47,XXY karyotype, exhibit a unique and
complex cancer risk profile that differs significantly from the general male population.
This increased susceptibility is not uniform across all cancer types but is highly
specific to certain malignancies, largely due to the hormonal, immunological, and
genetic consequences of the extra X chromosome.[7] Regarding solid tumor malignancies; the most striking association is the dramatically
elevated risk for male breast cancer. Men with KS have been reported to have a 40-
to 50-fold increased risk of developing this rare cancer. The primary driver of this
is the hormonal imbalance characteristic of KS, specifically the elevated serum Estrogen
and reduced testosterone levels, which promote the proliferation of mammary ductal
tissue and create an environment conducive to carcinogenesis.
Another notable risk is for extragonadal GCTs,[8] with men with KS having up to 50-fold increased risk, particularly for those arising
in the mediastinum (the space between the lungs). These tumors are thought to originate
from misplaced embryonic germ cells, and the extra X chromosome may play a direct
role in their development. In contrast, the risk for prostate cancer appears to be
decreased in men with KS, likely due to the inherent hypogonadism and chronically
low testosterone levels typical of the syndrome.[9] However, this protective effect may be lost if the patient undergoes testosterone
replacement therapy. Some studies also suggest a possible increased risk for other
tumors, such as lung cancer, though the evidence is less conclusive than for breast
cancer and GCTs.[10]
Knowledge Gap and Rationale
Knowledge Gap and Rationale
While KS is increasingly recognized for its association with various malignancies,
the precise mechanisms underlying its link to hematologic cancers, particularly acute
leukemia, remain incompletely understood. Existing literature, primarily consisting
of isolated case reports, does not provide a comprehensive epidemiological or pathophysiological
basis for this association.[11] Specifically, the role of chromosomal instability, X-linked gene dosage effects,
and hormonal imbalances in driving leukemogenesis in KS patients requires further
investigation. The diversity of leukemia subtypes observed in these cases (myeloid
vs. lymphoid) further highlights the need for a more detailed understanding of how
the 47,XXY karyotype influences different hematopoietic lineages.[12]
The present case report is rationalized by the scarcity of documented cases describing
the co-occurrence of acute leukemia and KS. By detailing two distinct presentations—one
with acute myeloid leukemia (AML) and another with B-cell acute lymphoblastic leukemia
(B-ALL)—this report provides valuable clinical and cytogenetic data directly relevant
to this knowledge gap. These cases, analyzed alongside a review of existing literature,
aim to deepen the understanding of the clinical features, cytogenetic complexities,
and potential shared pathophysiological mechanisms that may link these two conditions.
The report underscores the importance of cytogenetic analysis in young male patients
with leukemia, as it may lead to the incidental diagnosis of KS, which has significant
implications for both treatment and long-term care.[13]
Case Details
Case 1: AML-M4 in a 22-Year-Old Male Patient
Clinical presentation: A 22-year-old male patient presented with severe fatigue, generalized weakness,
and a suspected infection.
Laboratory findings: Hematological examination showed severe anemia (Hb: 5.1 g/dL), leukocytosis (white
blood cell: 35.32 ×103/μL), thrombocytopenia (22 × 103/μL), and 70% circulating blasts on peripheral smear. Bone marrow aspiration was hypercellular,
with 88% blasts exhibiting high nuclear-to-cytoplasmic ratios and granular cytoplasm.
Erythroid and myeloid precursors were severely suppressed, and megakaryocytes were
not seen.
Flow cytometry: Flow cytometry was conclusive of AML with AML-M4, with blasts positive for MPO (93%),
CD13 (71%), CD33 (81%), CD117 (86%), CD64 (63%), CD15 (36%), HLA-DR (76%), and CD34
(50%), and aberrant Expression of CD7 (74%).
Cytogenetics: Cytogenetic analysis by G-banding using trypsin and Giemsa (GTG) banding showed
a uniform 47, XXYc karyotype in 20 metaphases, making a diagnosis of KS. FISH testing
for AML1-ETO and CBFB rearrangements was negative, ruling out prevalent AML-associated
translocations.
Diagnosis: AML with AML-M4
Timeline: Bone marrow examination was performed on Day 4 after admission. Since cytogenetic testing is part of this examination to analyze chromosomes, it
was carried out on day 5. This placed the testing at the beginning of the diagnostic
process, which simultaneously confirmed the leukemia and led to the discovery of the
underlying KS.
Case 2: B-ALL in a 19-Year-Old Male Patient
Clinical presentation: A 19-year-old male patient was hospitalized with symptoms of weakness, fever, and
abdominal pain.
Laboratory findings: Bone marrow aspirate showed hypercellularity with 90% blasts, suppression of the
myeloid and erythroid series, and absence of megakaryocytes. There was significant
pancytopenia with severely low hemoglobin and red blood cell count (4.9 − 5.1 g/dL),
and critically low platelets (22 − 27 × 103 Cells/µL). Marked leukocytosis was observed
with a very high white blood cell count (35.32 − 93.18 × 103 cells/µL). The manual
differential count explicitly noted 70% blast cells, a key diagnostic feature of acute
leukemia.
Flow cytometry: Immunophenotypic analysis established the diagnosis of B-ALL, with positive expression
of CD19 (84%) and CD79a (45%), and positive expression of CD34 (87%) and HLA-DR (76%),
but negative for myeloid markers.
Cytogenetics: Cytogenetic analysis identified a mosaic karyotype: 48, XXYc, +5 in 15 and 46, XY
in 10 metaphases, representing KS and trisomy 5 in a leukemic subclone. FISH for gene
BCR-ABL and MLL gene rearrangements was negative, further narrowing the genetic characterization
of the disease.
Diagnosis: B-ALL (B-Cell Acute Lymphoblastic Leukemia)
Timeline: The patient was admitted on day 1 and the cytogenetic testing was performed on day
2 after admission, concurrent with the bone marrow examination. This crucial diagnostic step allowed
for the simultaneous diagnosis of both the acute leukemia subtype and the underlying
KS, enabling clinicians to tailor the treatment plan based on a complete understanding
of the patient's condition.
The institutional review board approved the present study, and the patient's general
consent was obtained.
Shared Pathophysiological Thread
Shared Pathophysiological Thread
The two cases, AML-M4 and B-ALL, share a common pathophysiological thread rooted in
the underlying KS. Both patients' karyotypes exhibit the presence of an extra X chromosome—47,XXYc
in Case 1 and 48,XXYc, + 5 in Case 2—indicative of genetic instability. This instability,
a hallmark of KS, likely contributes to the chromosomal abnormalities seen in both
leukemias. Furthermore, the impaired hematopoiesis observed in both cases, manifesting
as myeloid dysplasia in Case 1 and lymphoid hyperplasia in Case 2, points to broader
stem cell dysfunction related to KS. Both cases occur within the context of KS-related
hypogonadism, where reduced testosterone levels may impair normal immune and marrow
regulation, creating a permissive environment for malignancy. While immune dysregulation
was more prominent in the B-ALL case, KS patients are known to have altered T- and
B-cell immunity, suggesting that this shared feature may be a contributing factor
in both presentations ([Table 1]).
Table 1
Shared pathophysiological thread
|
Feature
|
AML-M4[*] (Case 1)
|
B-ALL[*] (Case 2)
|
Common KS[*]-related Implications
|
|
Karyotype
|
47,XXYc[*][20]
|
48,XXYc, + 5[15]/46,XY[10]
|
Genetic instability
|
|
Hematopoiesis
|
Myeloid dysplasia
|
Lymphoid hyperplasia
|
Stem cell dysfunction
|
|
Hormonal context
|
Hypogonadism (presumed in KS)
|
Hypogonadism (KS)
|
Reduced testosterone may impair normal immune and marrow regulation
|
|
Immune dysregulation
|
Less prominent
|
More prominent in ALL[*]
|
KS patients have altered T- and B-cell immunity
|
Abbreviations: AML-M4, acute myelomonocytic leukemia; B-ALL, B-cell acute lymphoblastic
leukemia; KS, Klinefelter syndrome; 47,XXYc, 47,XXY constitutional.
Note: “*”Immune dysregulation appears more prominent in ALL because its lymphoid malignancy
directly disrupts and remodels the already altered immune microenvironment from Klinefelter
syndrome and hypogonadism.
Cytogenetic Analysis
Cytogenetic analysis was performed on bone marrow aspirates and peripheral blood lymphocyte
cultures from both patients using the GTG-banding technique. For each bone marrow
sample, well-spread metaphases were examined microscopically to determine the karyotype.
Subsequently, peripheral blood lymphocyte cultures were performed using standard cytogenetic
protocols to differentiate between constitutional and acquired chromosomal abnormalities.
The lymphocytes were cultured, harvested, and stained, and a consistent number of
metaphases were analyzed to confirm the constitutional nature of the observed chromosomal
complements.
Case 1: Cytogenetic analysis of the bone marrow sample from Case 1 revealed a uniform karyotype
of 47,XXYc in all 20 metaphases analyzed ([Fig. 1]). This finding, diagnostic of KS, was further confirmed by a consistent 47,XXYc
karyotype in a subsequent peripheral blood lymphocyte culture, verifying the constitutional
nature of the chromosomal abnormality.
Fig. 1 Representative images of conventional cytogenetic results of GTG banded karyotype
showing 47,XXYc { Case 1} (A) karyotype image and (B) metaphase indicating an Extra X chromosome. GTG, G-banding using trypsin and Giemsa.
Case 2: Cytogenetic analysis of the bone marrow sample showed two distinct cell lines. Fifteen
of the 25 metaphases analyzed revealed an abnormal karyotype of 48,XXYc, + 5, consistent
with KS and an additional trisomy 5 ([Fig. 2]). The remaining 10 metaphases showed a normal male karyotype of 46,XY. Analysis
of a peripheral blood lymphocyte culture confirmed the constitutional 47,XXYc karyotype,
and the absence of trisomy 5 in this sample confirmed the acquired (neoplastic) nature
of the trisomy 5 clone.
Fig. 2 Representative images of conventional cytogenetic results of GTG banded karyotype
showing 48,XXYc, + 5 { Case 2} (A) Karyotype image and (B) Metaphase which indicates an extra copy of X chromosome with trisomy 5. GTG, G-banding
using trypsin and Giemsa.
Discussion
KS is the most prevalent sex chromosome aneuploidy in males, cytogenetically defined
by the presence of one or more supernumerary X chromosomes, most commonly resulting
in a 47,XXY karyotype. This chromosomal disorder occurs in approximately 1 in 600
live male births and presents with high phenotypic variability, including hypergonadotropic
hypogonadism, infertility, tall stature, gynecomastia, and cognitive or behavioral
challenges.[14] Although KS is relatively common, it is significantly underdiagnosed—clinical identification
is achieved in only 25 to –30% of cases, primarily due to its subtle and variable
presentation.[15]
Cytogenetically, KS represents a constitutional chromosomal abnormality that may influence
hematopoiesis through gene dosage effects and genomic instability. Overexpression
of genes located in the pseudoautosomal regions (PAR1 and PAR2) of the extra X chromosome,
which escape X-inactivation, may affect the transcription of genes involved in immune
regulation and cell cycle control, thereby promoting a tumorigenic environment.[16] In the first presented case, conventional cytogenetic analysis of bone marrow revealed
a 47,XXY karyotype in all 20 metaphases analyzed, without evidence of acquired chromosomal
changes. This confirmed the presence of a constitutional aneuploidy rather than a
leukemic clone. However, even in the absence of acquired abnormalities, constitutional
chromosomal imbalances such as those seen in KS have been associated with increased
susceptibility to hematologic malignancies due to ongoing genomic stress and immune
dysfunction. Additionally, research suggests that sex chromosome abnormalities, particularly
involving the X chromosome, may contribute to leukemogenic risk in younger individuals
with bone marrow failure syndromes or unexplained cytopenias.[17]
The second case was cytogenetically more complex, with mosaicism involving two cell
lines: 48,XXY, + 5 in 15 metaphases and a normal male karyotype (46,XY) in 10 metaphases.
Trisomy 5 is a recognized acquired cytogenetic aberration often seen in both myeloid
and lymphoid neoplasms, and it is associated with poor prognosis in some leukemia
subtypes.[11] The co-occurrence of KS and trisomy 5 supports the theory that individuals with
constitutional chromosomal aberrations may have an increased propensity for acquiring
leukemogenic somatic abnormalities. Mosaicism further underscores the importance of
analyzing an adequate number of metaphases to differentiate between inherited and
acquired changes.[18]
The risk for hematologic malignancies is also significantly heightened in men with
KS. A strong association has been established with non-Hodgkin lymphoma, for which
men with KS have a three- to four-fold increased risk. The exact mechanism for this
is not fully understood, but it is speculated to be related to the immune system dysfunction
and the potential for increased genomic instability resulting from the extra X chromosome.[19] The link to leukemia is less certain; while some studies have reported an increased
risk, others suggest that the association may be coincidental, with the KS diagnosis
made during the cytogenetic evaluation for leukemia.[20]
The presence of Trisomy 5 in a subset of the leukemic cells in Case 2 is a significant
finding. While the constitutional 47,XXY karyotype of KS is a predisposing factor
for hematologic malignancies, it is the acquired clonal abnormalities, such as trisomy
5, that directly influence the prognosis.[21] The findings in Case 2 align with patterns reported in the Mitelman Database, where
trisomy 5—although uncommon—has been documented as a recurrent acquired abnormality
in acute leukemia, particularly in aggressive or complex karyotypes.[22] In the context of B-ALL, trisomy 5 is a common chromosomal aberration; however,
its specific prognostic impact can be complex and depends on the presence of other
concurrent genetic abnormalities. Generally, the presence of multiple chromosomal
aberrations often suggests a more aggressive disease course and may be associated
with a less favorable outcome compared to cases with a normal karyotype or a single,
simple chromosomal change.[23] A comparison of the literature review of KS with AML and B-ALL is provided in [Table 2].
Table 2
Cytogenetic and clinical characteristics of reported leukemia cases in patients with
Klinefelter syndrome
|
Author, Year
|
Age/ex
|
Leukemia subtype
|
KS karyotype
|
Additional cytogenetics
|
Treatment
|
Outcome/note
|
|
Slavcheva et al, 2010[8]
|
41 M
|
AML-M4 (myelomonocytic)
|
47,XXY
|
t(8;21)(q22;q22)
|
Induction chemotherapy
|
Achieved remission
|
|
Lim et al, 2010[24]
|
Adult M
|
AML with RUNX1:RUNX1T1
|
47,XXY
|
t(8;21)(q22;q22)
|
Standard AML induction
|
Association of KS with recurrent AML lesion
|
|
Ljubić et al, 2010[25]
|
Adult M
|
Acute basophilic leukemia (AML subtype)
|
47,XXY
|
None specific
|
AML protocol
|
First KS case with this rare AML subtype
|
|
Kjeldsen, 2022[26]
|
3 M
|
B-ALL
|
47,XXY
|
≥2 acquired aberrations; shortened telomeres
|
Standard ALL therapy
|
Highlighted chromosomal instability in KS + ALL
|
|
Gürgey et al, 1994 (series)[27]
|
Children (various M)
|
B-ALL/ALL
|
47,XXY (some mosaic)
|
Variable (extra aberrations in several cases)
|
Pediatric ALL protocols
|
Several pediatric ALL cases in KS summarized
|
Abbreviations: AML, acute myeloid leukemia; KS, Klinefelter syndrome.
The key interaction here is that the underlying genetic instability of KS (due to
the extra X chromosome) likely creates a permissive environment for the development
of these secondary neoplastic chromosomal aberrations, such as Trisomy 5. This suggests
that KS itself does not directly worsen the prognosis in the same way that a high-risk
mutation would, but it contributes to the development of the aggressive clonal abnormalities
that do have a negative prognostic impact.[13] This unique combination of sex chromosome aneuploidy and a recurrent leukemic abnormality
may have a synergistic leukemogenic effect, particularly on the lymphoid lineage—as
seen in this case of B-ALL. Testosterone deficiency in KS has also been implicated
in altering the bone marrow microenvironment and impairing hematopoietic stem cell
function and immune surveillance, thus facilitating clonal evolution and malignant
transformation. These genetic and hormonal disruptions are believed to play a central
role in both the initiation and aggressiveness of hematologic malignancies in KS patients.[12] Altogether, these findings highlight the clinical importance of performing cytogenetic
testing in young male patients who present with hematologic malignancies and clinical
features suggestive of KS—such as gonadal dysfunction, tall stature, or neurodevelopmental
delays.
Conclusion
Both cases highlight a possible association between KS and acute Leukemia development,
which is most likely the result of chromosomal instability induced by the extra X
chromosome. This evidence supports a multidisciplinary approach and emphasizes the
need for additional studies to define the role of KS in leukemia predisposition. Cytogenetic
analysis is crucial for both diagnosing leukemia and uncovering underlying constitutional
chromosomal disorders like KS. This dual function provides essential information for
patient counseling, risk stratification, and long-term care.
