Introduction: Glutamate-cysteine ligase catalytic subunit (GCLC), previously known as gamma-glutamyl-cysteine synthetase, is an essential rate-limiting step in glutathione synthesis. Glutathione modulates multitudes of critical cellular processes and scavenges free radicals. Its deficiency is reported to cause hemolysis of variable severity and is a rare cause of neurological abnormalities such as spinocerebellar ataxia. Clinical Presentation: We report a 55-year-old female patient with progressive late-onset ataxia, lower limb spasticity, and chronic hemolytic anemia found to have a GCLC pathogenic variant and low glutathione level. Magnetic resonance imaging of the head and cervical spine showed global cerebellar atrophy with widened folia and decreased diameter of the upper cervical spine. Blood workup revealed hemolytic anemia with genetic testing confirmed a homozygous variant, c.514 T>A in exon 4 of the GCLC gene, resulting in Ser172Thr (TCC>ACC). Management encompassed a multidisciplinary approach with a trial of high-dose alpha-lipoic acid, glutathione supplement, and physical therapy. Conclusions: GCLC deficiency manifesting with hemolysis has been reported in 12 cases worldwide from 6 independent families, with only 4 cases having additional neurological manifestations. To date, no specific GCLC gene mutation has been attributed to the reported neurological constellation of symptoms. To the best of our knowledge, this is the first case report of late-onset spinocerebellar degeneration as a manifestation of c.514T>A (p. S172T) GCLC pathological variant genetic mutation.

Established Facts

  • Glutamate-cysteine ligase catalytic subunit (GCLC) deficiency is reported to cause hemolysis and spinocerebellar ataxia.

  • GCLC gene mutation is an autosomal recessive biallelic mutation.

  • Previously reported mutations encompassing c.379C > T (p.R127C), c.1109A > T (p.H370L), c.473C > T (p.P158L), c.1241C > T (p.P414L), c.1772G > A (p.S591N), c.514T > A (p.S172T).

Novel Insights

  • Novel pathological variant genetic mutation of GCLC c.514T>A (p. S172T) as a cause of late-onset spinocerebellar degeneration and hemolysis.

Glutathione (GSH) was first discovered in mammalian cells in the 1980s based on drug metabolism and detoxification in the liver [1]. It retains a significant biological role in deoxyribonucleic acid gene expression, detoxifying xenobiotics, the proliferation of brain cells, and a pivotal scavenger of reactive oxygen species [2]. GSH is a tripeptide molecule (glutamate, cysteine, and glycine) produced via ATP-dependent sequential reactions. The first step is catalyzed by γ-glutamylcysteine and GSH synthetase [1]. The described mutation affects gamma-glutamyl cysteine synthase, and glutathione synthetase deficiency is an inborn error of GSH metabolism. The latter can manifest with a constellation of hemolytic anemia alone or with acidosis and central nervous system impairment [3]. Human glutamate cysteine ligase is a heterodimer comprised a catalytic (GCLC) and a regulatory subunit (GCLM), for which systemic manifestation has been observed in their mutations [3]. GCLC deficiency (OMIM #230450) is a rare disease to cause hemolysis of variable severity and sometimes associated with neurological abnormalities [2]. There are only twelve reported cases worldwide to cause hemolytic anemia; four reported co-current neurological symptoms; two siblings with peripheral neuropathy, myopathy, and spinocerebellar degeneration; another with spinocerebellar degeneration symptoms; one with a learning disability; and lastly, one with psychomotor developmental delay and neuropathy. We report the first case of late-onset spinocerebellar degeneration due to autosomal recessive homozygous variant mutation of GCLC with chronic compensated hemolytic anemia [p.(Ser172Thr) (TCC>ACC): c.514 T>A in exon 4 of the GCLC gene (NM_001498.3)].

A 55-year-old right-handed female with a medical history of bronchial asthma was referred to the neurology clinic with 5-year history of progressive lower limb stiffness and unsteady gait. Initially, she noted gradual progressive stiffness in her lower limb over 5 years with a tendency to fall due to unsteadiness that warranted using a walking aid. Over the past 2 years, she has been mainly wheelchair-bound. She did not note stiffness elsewhere, no diplopia, dysphonia, dysarthria, or hand tremor. She is a product of normal vaginal delivery of third-degree consanguineous parents with an unremarkable family history of no reported hemolytic or neurological diseases. A review of the system was unremarkable, with no relevant constitutional symptoms. She is a school teacher without exposure to heavy metals, recreational drugs, or alcohol.

Initial vitals were within normal parameters; a temperature of 36.4°C, respiratory rate of 17 breaths per minute, oxygen saturation of 98% on room air, and blood pressure of 129/62 mm Hg with no orthostatic component. On general inspection, there was no noted dysmorphism with below-average height to her family of a height of 145 cm with a body mass index of 52.3 (weight 124 kg), hyperlordosis, and mild scoliosis. Higher functional status revealed no cognitive dysfunction (mini-mental state examination, MMSE 28). Neurological examination was remarkable for bilateral ocular saccadic intrusions, with no gaze-evoked nystagmus. There was spasticity in the lower limb with enhanced deep tendon reflexes in the lower limbs associated with bilateral Babiniski’s and Chaddock sign. A cerebellar exam is remarkable for bilateral ocular saccadic intrusions, wide-based ataxic gait, and inability to tandem with bilateral dysmetria. She showed remarkable positive Romberg’s sign suggestive of deep sensory impairment in the lower extremities. Overall, baseline functional status of the patient is measured using modified Rankin score of 3 (mRS) with using wheelchair most of the time due to unsteadiness and lower limb spasticity.

Blood workup revealed low hemoglobin (Hb), 10.6 gm/dL, high retic count (256.3 × 103/μL) and retic % (8.1%), normal platelet 186 × 103/μL, low haptoglobin <10 mg/dL, LDH (434 U/L). Iron studies were normal. Peripheral smear showed mild anemia with dimorphism, anisopoikilocytosis, and fragmented and teardrop red blood cells (RBCs). Hb electrophoresis and glucose 6-phosphate dehydrogenase (G6PD) levels were normal. Negative autoimmune workup and direct antiglobulin test (DAT), suggestive of chronic compensated hemolytic anemia. HbA1c was constantly 4% influenced by chronic hemolysis. Vitamin B12, thyroid function, vitamin E, B1, and pyridoxine were within normal parameters. GSH level 6.2 mg/dL RBC (46.9–90.1). The paraneoplastic panel performed in the Mayo clinic is unremarkable, with no anti-GAD 65 or anti-amphiphysin antibodies that could manifest with stiff person syndrome.

Ultrasound abdomen showed a liver span of 15.8 cm, mild fatty liver changes, and a normal-sized spleen measuring about 9.4 cm in bipolar diameter. Magnetic resonance imaging brain and cervical-thoracic spine with contrast, axial, and midsagittal FLAIR shows diffuse cerebellar volume loss with prominent cerebellar folia suggestive of mild cerebellar atrophy brainstem and upper cervical cord atrophy shown in Figure 1a, b. Normal nerve conduction study and electromyography.

Fig. 1.

a, b Magnetic resonance imaging (MRI) brain and cervical-thoracic spine with contrast, axial, and midsagittal FLAIR shows diffuse cerebellar volume loss with prominent cerebellar folia suggestive of mild cerebellar atrophy brainstem and upper cervical cord atrophy.

Fig. 1.

a, b Magnetic resonance imaging (MRI) brain and cervical-thoracic spine with contrast, axial, and midsagittal FLAIR shows diffuse cerebellar volume loss with prominent cerebellar folia suggestive of mild cerebellar atrophy brainstem and upper cervical cord atrophy.

Close modal

Management encompassed a multidisciplinary approach, with a high dose of alpha-lipoic acid 600 mg twice daily orally, GSH 250 mg twice daily orally, and folate 5 mg daily orally. She is undergoing intensive physical therapy targeting spasticity with routine hematology and neurology clinic follow-up.

Further genetic testing of whole exome sequence analysis revealed a pathogenic gene variant of GCLC gene as autosomal recessive homozygous mutation of glutamyl-cysteine synthetase deficiency [c.514T>A (p. S172T (TCC>ACC) on exon 4 (NM_001498.3)].

Glutamate-cysteine ligase catalytic subunit (GCLC), previously known as gamma-glutamylcysteine synthetase (γ-GCS), catalyzes the first and rate-limiting step in synthesizing GSH, with its deficiency being rarely reported worldwide. It makes understanding and establishing its spectrum of clinical manifestation limited. From a biochemical standpoint, GSH concentration in the brain is variable, with the highest concentration in the cortex, followed by the cerebellum, and its lowest levels in the substantia nigra [1]. GSH is a significant thiol redox buffer; it involves S-glutathionylation protein, an imperative adaptive cellular response to protect protein functions in the cell from oxidative stress, which is thought to be a crucial key factor in protection against neurodegeneration [1, 4].

On a note of comparison, GSH is an essential intracellular antioxidant, with variable degrees of glutathione synthetase mutations that correlate to residual activity and stability of GSH [4]. For instance, milder forms manifest with a residual yet unstable GSH molecule, causing the mild phenotypical manifestation of hemolysis due to erythrocytes’ susceptibility to oxidative stress compared to absolute GSH deficiency, which accounts for further multisystem organ manifestations from damage implicant by free-radical [4‒8].

GCLC enzymatic reaction consists of a catalytic subunit encoded by GCLS and a regulatory subunit by GCLM [6]. The degree of residual erythrocyte GSH activity contributes to the extent of hemolytic anemia, with severe cases exhibiting neurological findings [6]. The previously described 12 patients from six unrelated families had erythrocyte GSH <5% of normal mean and GCL activity <10% of normal mean manifestation; however, their hemolytic anemia was of variable severity and age of onset [5, 6, 8]. Some manifested as neonatal jaundice requiring exchange transfusion, while others had milder forms of chronic compensated hemolytic anemia with episodes of jaundice in adolescence [8]. Such observation raises the possibility of possible co-founding genetic mutation or other pathophysiology beyond to be explained only by residual enzyme activity and severity of phenotypical presentation.

To date, neurological manifestations in GCL mutation are heterogeneous and follow no specific pattern, nor a specific implicated variant of the described gene is known. Konard et al. [6] in 1972 reported the first neurological manifestation in γ-GCS deficiency of two siblings on non-consanguineous parents with compensated hemolytic anemia and spinocerebellar degeneration symptoms with 7% GCLC activity (percentage of normal mean). In subsequent 2 years, Richards et al. [7] reported two other siblings with hemolytic anemia but multiple peripheral and central nervous system manifestations (oxoprolinuria and myopathy, peripheral neuropathy, and spinocerebellar degeneration) with γ-GCS deficiency, raising the question of possible multiple genetic mutations of the same gene of local RBC effect (hemolysis) versus generalized implication [5, 7]. In 1999, Beutler et al. [9] reported 14-year-old with hemolytic anemia and neonatal jaundice with a learning disability and no other neurological features. In 2007, a reported case of residual 1% GCLC activity had co-current psychomotor developmental delay and neuropathy [9, 10]. The last reported paper in 2017 of GCLC gene mutation in six children of two independent families with hemolytic anemia exhibited no neurological findings, even though one of these families showed a genetic variant similar to our current reported case (Ser172Thr) (TCC>ACC): c.514 T>A in exon 4 [8]. However, due to the early diagnosis age in these cases, a follow-up would be paramount to understanding the possible implications of late-onset neurological features.

GCLC gene mutation is an autosomal recessive biallelic with previously reported mutations encompassing c.379C > T (p.R127C), c.1109A > T (p.H370L), c.473C > T (p.P158L), c.1241C > T (p.P414L), c.1772G > A (p.S591N), c.514T > A (p.S172T). As in the previous 4 cases with neurological constellations, no specific variant mutation of the GCLC gene was identified as the culprit. Our patient was found to have GCLC mutation variant c.514 T>A in exon 4, which was reported in three consanguineous family patients with only hemolytic anemia and no neurological symptoms [8].

The observed wide array of neurological manifestations in GCLC mutation; one cannot disregard the possibility of rare pleomorphic genetic variants contributing to heterogeneous presentations and age of onset. GCLC activity alone cannot explain the variable neurological phenotypical symptoms. Previously reported cases of residual 1% GCLC activity had no neurological findings compared to a patient with residual 7% GCLC activity exhibiting spinocerebellar degeneration symptoms as opposed to what is observed in glutathione synthetase deficiency [8]. Due to the rarity of GCLC deficiency, limited reported cases, and scarcity of studies on implicated variants, further genetic and molecular studies are warranted to understand the pathophysiology of such a rare disease entity which could aid in a better understanding of possible gene therapy and prognosis.

Due to the scarcity of reports on GCLC deficiency presenting with late-onset spinocerebellar degeneration, neurologists and hematologists must consider the rare inborn error of GSH metabolism as a cause of this constellation of symptoms.

The authors would like to thank Qatar National Library (QNL) for this publication’s funding.

This case report was approved by the Hamad Medical Corporation’s Medical Research Center (protocol number: MRC-04-22-104). Written informed consent was obtained from the patient for publication for this case report, any accompanying images, and photography.

The authors have no conflict of interest to disclose.

Qatar National Library funded the open access publication fees of this case.

Writing the initial draft of the manuscript: A.S.S., M.A. and M.A.A.; conceptualization and supervision and medical management of the case: M.A. and M.A.A.; and revising the manuscript critically and literature review: A.S.S., M.A., and M.S.

The datasets used and/or analyzed during the current study are available from the corresponding author on request.

1.
Aoyama
K
,
Nakaki
T
.
Impaired glutathione synthesis in neurodegeneration
.
Int J Mol Sci
.
2013
;
14
(
10
):
21021
44
.
2.
Glutathione Synthetase Deficiency [Internet]
.
Medscape.com
;
2021
. [cited 2021 Dec 14]. Available from: https://emedicine.medscape.com/article/944368-overview.
3.
Xia
H
,
Ye
J
,
Wang
L
,
Zhu
J
,
He
Z
.
A case of severe glutathione synthetase deficiency with novel GSS mutations
.
Braz J Med Biol Res
.
2018
;
51
(
3
):
e6853
.
4.
Johnson
WM
,
Wilson-Delfosse
AL
,
Mieyal
JJ
.
Dysregulation of glutathione homeostasis in neurodegenerative diseases
.
Nutrients
.
2012
;
4
(
10
):
1399
440
.
5.
Beutler
E
,
Moroose
R
,
Kramer
L
,
Gelbart
T
,
Forman
L
.
Gamma-glutamylcysteine synthetase deficiency and hemolytic anemia
.
Blood
.
1990
;
75
(
1
):
271
3
.
6.
Konrad
PN
,
Richards
F
2nd
,
Valentine
WN
,
Paglia
DE
.
Glutamyl-cysteine synthetase deficiency. A cause of hereditary hemolytic anemia
.
N Engl J Med
.
1972
;
286
(
11
):
557
61
.
7.
Richards
F
,
Cooper
MR
,
Pearce
LA
,
Cowan
RJ
,
Spurr
CL
.
Familial spinocerebellar degeneration, hemolytic anemia, and glutathione deficiency
.
Arch Intern Med
.
1974
;
134
(
3
):
534
7
.
8.
Almusafri
F
,
Elamin
HE
,
Khalaf
TE
,
Ali
A
,
Ben-Omran
T
,
El-Hattab
AW
.
Clinical and molecular characterization of 6 children with glutamate-cysteine ligase deficiency causing hemolytic anemia
.
Blood Cells Mol Dis
.
2017
;
65
:
73
7
.
9.
Beutler
E
,
Gelbart
T
,
Kondo
T
,
Matsunaga
AT
.
The molecular basis of a case of γ-glutamylcysteine synthetase deficiency
.
Blood
.
1999
;
94
(
8
):
2890
4
.
10.
Mañú Pereira
M
,
Gelbart
T
,
Ristoff
E
,
Crain
KC
,
Bergua
JM
,
López Lafuente
A
, et al
.
Chronic non-spherocytic hemolytic anemia associated with severe neurological disease due to gamma-glutamylcysteine synthetase deficiency in a patient of Moroccan origin
.
Haematologica
.
2007
;
92
(
11
):
e102
5
.