Muscular dystrophies (MDs) are a heterogeneous group of inherited myopathies that share similar clinical features and dystrophic changes on muscle biopsies [
Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and lactic dehydrogenase (LDH) are components of routine or comprehensive blood panels and collectively demonstrate liver function. Consequently, in apparently healthy children, analysis of these liver enzymes is performed more frequently than analysis of creatine kinase (CK), a more specific marker of muscle disease [
With advancements in diagnostic methodologies, such as magnetic resonance imaging (MRI), muscle biopsy, and genetic screening, more types of MD can be categorized accurately. However, because not all hospitals have access to these advanced techniques, the diagnosis of MD can still be challenging. CK values may facilitate differential diagnosis to some extent [
Therefore, in this study, we retrospectively reviewed the clinical records of hundreds of Chinese patients with MD, in order to examine changes in enzyme profiles in different types of MD. Our results emphasize that a diagnosis of occult muscle disease should be considered when confronted with an unexplained elevation of serum enzymes.
Clinical data from Chinese patients with MD who visited the Department of Neurology at the First Affiliated Hospital of Sun Yat-sen University were collected between June 2012 and October 2013. Patients were excluded if they had any coexisting medical diseases according to medical records. This study was approved by the Local Ethical Committee at Sun Yat-sen University (China) and was conducted in accordance with the recommendations of the Declaration of Helsinki. Adult patients and parents of affected children provided written informed consent.
Patients had been diagnosed with one of the following five pathologies: (1) Duchenne muscular dystrophy, (2) Becker’s muscular dystrophy (BMD), (3) facioscapulohumeral dystrophy (FSHD), (4) limb girdle muscular dystrophy (LGMD), or (5) Emery-Dreifuss muscular dystrophy (EDMD). For DMD/BMD, patients were diagnosed by dystrophin gene analysis or immunohistochemistry and western blotting for dystrophin on muscular biopsy specimen. FSHD was confirmed by two neurologists on the basis of clinical manifestation. LGMD was identified according to traditional clinical, electrophysiological, and histological criteria, and diagnoses of DMD/BMD, FSHD, polymyositis, and myotonic dystrophy were excluded simultaneously. Some cases of LGMD were confirmed by gene analysis. EDMD was diagnosed according to previously published criteria [
Serum enzymes, including ALT, AST, ALP, LDH, and CK, were measured using an Abbott Aeroset fully automatic biochemical analyzer (Abbott Laboratories, USA). The levels of serum enzymes were assayed according to the instructions provided with the corresponding enzymatic kits. The upper limits of normal for ALT, AST, ALP, LHD, and CK were 40, 37, 110, 240, and 250 U/L, respectively.
Statistical analysis was performed using SPSS, Version 20.0 (IBM SPSS Statistics 20.0). Due to the differences in the normal ranges of different enzymes, new variables were adopted appropriately for analysis; variables ALTn, ASTn, ALPn, and LDHn were defined as the value of the enzyme divided by the upper limit of normal (ULN) for that enzyme. The normal distributions of the variables were tested with the Kolmogorov-Smirnov test (
A total of 232 patients were included in this study, of which 120 patients were diagnosed with DMD, 36 patients were diagnosed with BMD, 19 were diagnosed with FSHD, 46 were diagnosed with LGMD, and 11 were diagnosed with EDMD. The mean age of patients with DMD was the lowest of all subtypes (~7 years), while the mean age of patients with FSHD was the highest of all subtypes (~26 years). More than 97% of patients with DMD and BMD had abnormal ALT, AST, and LDH values. The proportion of patients with abnormal ALT and AST values was lowest in patients with EDMD (27.3% and 36.4%, resp.). More than 40% of patients with FSHD and LGMD had abnormal ALT, AST, ALP, and LDH values, with the exception of AST in FSHD, which was abnormal in less than 40% of patients (36.8%). The demographics and frequencies of patients with MD presenting with abnormal serum enzymes are shown in Table
The demography and frequency of patients with MD presented with normal or abnormal serum enzymes levels.
Category | Age (y) | Gender |
ALTn |
ASTn |
ALPn |
LDHn |
CKn |
||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mean ± SD (range) | Male | Female | Normal | Abnormal | Normal | Abnormal | Normal | Abnormal | Normal | Abnormal | Normal | Abnormal | |
DMD | 6.7 ± 3.4 (7 m–24) | 120 (100) | 0 (0) | 3 (2.5) | 119 (97.5) | 3 (2.5) | 119 (97.5) | 39 (32) | 83 (68) | 3 (2.5) | 119 (97.5) | 0 (0) | 122 (100) |
BMD | 13.0 ± 8.5 (2–37) | 36 (100) | 0 (0) | 0 (0) | 37 (100) | 0 (0) | 37 (100) | 16 (43.2) | 21 (56.8) | 0 (0) | 37 (100) | 0 (0) | 37 (100) |
FSHD | 25.8 ± 9.3 (13–50) | 13 (68) | 6 (32) | 5 (26.3) | 14 (73.7) | 12 (63.2) | 7 (36.8) | 10 (52.6) | 9 (47.4) | 11 (57.9) | 8 (42.1) | 1 (5.3) | 18 (94.7) |
LGMD | 22.6 ± 11.4 (3–54) | 23 (56) | 18 (44) | 11 (26.8) | 30 (73.2) | 9 (22.0) | 32 (78.0) | 24 (58.5) | 17 (41.5) | 10 (24.4) | 31 (75.6) | 1 (2.4) | 40 (97.6) |
EDMD | 15.4 ± 9.9 (6–42) | 6 (55) | 5 (45) | 8 (72.7) | 3 (27.3) | 7 (63.6) | 4 (36.4) | 4 (36.4) | 7 (63.6) | 6 (54.5) | 5 (45.5) | 3 (27.3) | 8 (72.7) |
MD, muscular dystrophy; DMD, Duchenne muscular dystrophy; BMD, Becker’s muscular dystrophy; FSHD, facioscapulohumeral dystrophy; LGMD, limb girdle muscular dystrophy; EDMD, Emery-Dreifuss muscular dystrophy; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase; LDH, lactic dehydrogenase; CK, creatine kinase; m, month.
For ALT, AST, and LDH levels, patients with DMD had higher serum concentrations than patients with BMD, FSHD, LGMD, and EDMD (
Serum ALP profiles were different from those of the other three enzymes (ALT, AST, and LDH). Significant differences were only observed between patients with DMD and FSHD and between patients with DMD and LGMD (
Serum enzymes levels among five types of MD.
Category | ALTn ( |
ASTn ( |
ALPn ( |
LDHn ( |
CKn ( |
---|---|---|---|---|---|
DMD | 6.55 (4.85–8.18)b,c,d,e | 5.32 (3.98–6.68)b,c,d,e | 1.1 (0.94–1.25)c,d | 4.28 (3.23–5.60)b,c,d,e | 44.77 (31.05–56.57)b,c,d,e |
BMD | 2.91 (1.96–4.61)a,c,d,e | 2.85 (1.76–4.5)a,c,d,e | 1.06 ± 0.48 | 2.02 (1.49–3.48)a,c,d,e | 27.59 (16.64–41.22)a,c,d,e |
FSHD | 1.04 ± 0.48a,b | 1.00 (0.87–1.44)a,b,d | 0.60 (0.42–0.92)a | 1.02 (0.93–1.44)a,b | 3.05 (1.64–3.91)a,b,d |
LGMD | 1.65 (0.74–3.39)a,b,e | 1.68 (1.01–2.86)a,b,c,e | 0.55 (0.45–1.17)a | 1.49 (1.00–2.37)a,b | 9.08 (4.50–21.87)a,b,c,e |
EDMD | 0.50 (0.36–0.83)a,b,d | 0.73 (0.69–1.04)a,b,d | 1.15 ± 0.54 | 1.09 ± 0.17a,b | 1.64 (0.66–3.51)a,b,d |
|
92.45 | 111.09 | 22.83 | 112.19 | 114.01 |
|
<0.001 | <0.001 | <0.001 | <0.001 | <0.001 |
MD, muscular dystrophy; DMD, Duchenne muscular dystrophy; BMD, Becker’s muscular dystrophy; FSHD, facioscapulohumeral dystrophy; LGMD, limb girdle muscular dystrophy; EDMD, Emery-Dreifuss muscular dystrophy; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase; LDH, lactic dehydrogenase; CK, creatine kinase.
aComparing with DMD,
bComparing with BMD,
cComparing with FSHD,
dComparing with LGMD,
eComparing with EDMD,
For patients with different types of MD, only patients with DMD exhibited simultaneous elevation of serum ALT, AST, ALP, and LDH values. ALT levels exhibited the greatest increase, followed by AST, LDH, and ALP (Table
The serum enzymes profile in five types of MD.
Category | ALTn ( |
ASTn ( |
ALPn ( |
LDHn ( |
---|---|---|---|---|
BMD | 2.91 (1.96–4.61) (↑) | 2.85 (1.76–4.5) (↑) | 1.06 ± 0.46 (→) | 2.02 (1.49–3.48) (↑) |
DMD | 6.55 (4.85–8.18) (↑) | 5.32 (3.98–6.68) (↑) | 1.1 (0.94–1.25) (↑) | 4.28 (3.23–5.60) (↑) |
EDMD | 0.50 (0.36–0.83) (→) | 0.73 (0.69–1.04) (→) | 1.15 ± 0.54 (→) | 1.06 ± 0.19 (→) |
FSHD | 1.04 ± 0.48 (→) | 1.00 (0.87–1.44) (→) | 0.60 (0.42–0.92) (→) | 1.02 (0.93–1.44) (→) |
LGMD | 1.65 (0.74–3.39) (↑) | 1.68 (1.01–2.86) (↑) | 0.55 (0.45–1.17) (→) | 1.49 (1.00–2.37) (↑) |
MD, muscular dystrophy; DMD, Duchenne muscular dystrophy; BMD, Becker’s muscular dystrophy; FSHD, facioscapulohumeral dystrophy; LGMD, limb girdle muscular dystrophy; EDMD, Emery-Dreifuss muscular dystrophy; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase; LDH, lactic dehydrogenase.
“→” represents that patients had similar levels of enzymes comparing with normal people (
Elevated serum ALT, AST, and LDH values were observed in patients with BMD or LGMD (
The enzymes profile between patients with BMD and LGMD.
Category | ALTn ( |
ASTn ( |
ALPn ( |
LDHn ( |
---|---|---|---|---|
BMD | 2.91 (1.96–4.61) (↑) | 2.85 (1.76–4.5) (↑) | 1.06 ± 0.46 | 2.02 (1.49–3.48) (→) |
LGMD | 1.65 (0.74–3.39) (→) | 1.68 (1.01–2.86) (→) | 0.55 (0.45–1.17) | 1.49 (1.00–2.37) (→) |
BMD, Becker’s muscular dystrophy; LGMD, limb girdle muscular dystrophy; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase; LDH, lactic dehydrogenase.
“→” represents that patients had 2-fold ULN of enzymes levels (compared with “2,”
Patients with FSHD and EDMD exhibited the same profiles for the four liver enzymes, with all values remaining within the normal range (Table
Because age and gender were correlated with diagnosis, we developed discriminant functions to distinguish between BMD and LGMD more accurately without gene detection or muscle biopsy (Table
Discriminant functions to identify patients with BMD and LGMD.
Discriminant functions |
---|
|
|
BMD, Becker’s muscular dystrophy; LGMD, limb girdle muscular dystrophy; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase; LDH, lactic dehydrogenase.
Twenty-six patients with LGMD (over 50%) had genetic tests. Among them, five had duplicate genetic tests (data not shown). Three patients carried
Since there were few samples from patients with LGMD2A, we could not perform any statistical analysis to detect characteristic profiles of serum enzymes between patients with and without LGMD2A. There were no significant differences in ALT, AST, or LDH levels between patients with and without LGMD2B (data not shown). Additionally, no significant differences in CK levels were observed between patients with and without LGMD2B. However, ALP levels in LGMD2B patients (
Here, we presented a retrospective analysis of serum enzyme levels from patients with MD, who were originally diagnosed according to clinical and/or genetic diagnoses. Although serum CK testing is an easy, sensitive, and inexpensive test for muscular diseases, it appears to be underutilized in routine clinical practice. In apparently healthy children, aminotransferase levels are assessed more frequently than CK or aldolase levels [
In the present study, a high frequency of patients with MD presented with abnormal levels of serum enzymes (including ALT, AST, ALP, and LDH). For instance, all patients with BMD and up to 97% of patients with DMD had elevated ALT, AST, and LDH values. Even in patients with EDMD, for which the frequency was relatively small, the proportion of patients presenting with abnormal ALT, AST, or LDH values was no lower than 25%. Indeed, studies from around the world [
The mechanism through which levels of ALP and LDH become abnormal in patients with MD is still unknown. Elevations in ALT and AST levels are common indicators of hepatocellular damage; however, ALT abnormalities are also found in cardiac and skeletal muscle, although ALT activity in skeletal muscle is only one-tenth of that in hepatocytes [
Serum enzyme levels were elevated to variable degrees among patients with different subtypes of MD. McMillan et al. reported that ALT values are elevated by up to 22.6 times the ULN in patients with DMD [
To some extent, CK values may facilitate differential diagnosis [
Clinical differential diagnosis between BMD and LGMD may be difficult because the clinical phenotype of BMD tends to overlap with other limb girdle syndromes, especially LGMD [
LGMD is a heterogeneous genetically determined group of skeletal muscle disorders. Because at least 18 genetically distinct subtypes of LGMD have been described, determining the exact subtype of LGMD in a particular patient can be challenging [
Our study had several limitations. First, only 11 cases of EDMD and 19 cases of FSHD were reviewed in the present study. It is likely that the small sample studied is not representative of the general patient population. Second, not all the patients with LGMD were confirmed by genetic testing, and the exact diagnosis of LGMD subtypes was challenging. Third, we did not thoroughly investigate the effects of some medications or food on serum enzyme levels. Marked variability in serum enzymes can occur from day to day [
In summary, we found that a high frequency of patients with MD presented with abnormal serum enzyme levels. The characteristic profiles of serum enzymes facilitated the differentiation of MD subtypes. For example, DMD was characterized by simultaneous elevation of ALT, AST, LDH, and ALP; BMD and LGMD were characterized by elevation of ALT, AST, and LDH; and FSHD and EDMD lacked abnormalities in the serum levels of these four enzymes. To further differentiate BMD from LGMD, discriminant functions were developed for cases in which enzyme levels and age are known. For LGMD, patients with LGMD2B had significantly higher ALP levels than patients with non-LGMD2B subtypes. Thus, our approach makes it possible to determine the subtypes of MD by serum enzyme profiles prior to genetic testing, which will increase the chance that a mutation will be found in the first gene analyzed.
All authors declare that there is no conflict of interests regarding the publication of this paper.
Yuling Zhu and Huili Zhang contributed equally to the paper.
The authors are grateful to the patients and families who participated in the study. This research was supported by funding from the National Nature Science Foundation of China (no. 81271401), Joint Fund of National Nature Science Foundation of China, and Natural Science Foundation of Guangdong Province of China (no. U1032004).