Hypocupremia and bone marrow failure

Copper deficiency associated with neurological disorders isa well-documented condition. However, hypocupremia is less oftenrecognized as a cause of cytopenias or bone marrow failure.We report an illustrative series of three new cases of bi-lineagecytopenia associated with copper deficiency. We have analyzedclinical features of current and historical cases to identifyclues that could facilitate application of appropriate laboratorytesting and heighten the level of clinical suspicion. By maintainingan appropriately high level of suspicion for potential copperdeficiency and obtaining a serum copper level, bone marrow failuredue to this condition can be correctly diagnosed and treated.We suggest that copper deficiency be included in the differentialdiagnosis of reversible causes of bone marrow failure syndromesincluding myelodysplastic syndrome.

Key words: copper deficiency, hypocupremia, bone marrow failure.

Introduction

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Introduction

In the evaluation of patients with pancytopenia, reversiblecauses of bone marrow failure such as nutritional deficiencies,viral infections, and medications need to be considered in thedifferential diagnosis. Copper deficiency can be easily treatedbut the diagnosis may be difficult due to comorbidities andlow level of clinical suspicion.

Patients with copper deficiency most commonly present with neurologicaldisorders, including myeloneuropathy, arthralgias and neuropathy.^1–4A diagnosis of copper deficiency is usually established by measuringserum copper or ceruloplasmin levels; a serum copper level <10 ${propto}$ mol/L or ceruloplasmin <180 mg/L is considered presumptiveevidence of copper deficiency. The most common hematologic abnormalitiesassociated with copper deficiency include anemia and neutropenia,while the platelet count usually remains normal.

The adult diet in Western countries contains 0.6 to 1.6 mg ofcopper/d. Water, shellfish, organ meats, nuts, and grains areall sources of dietary copper. Absorption occurs through theintestinal mucosa across the basement membrane into the bloodstream via energy dependent mechanisms where the availabilityand saturation of copper may limit absorption. Of significantinterest is the physiologic relationship between copper andzinc. High zinc levels result in increased metallothionin productionin enterocytes. The high affinity of copper to metallothionindisplaces zinc and thus leads to the accumulation of copperin the enterocytes. The enterocytes are ultimately shed intothe gastrointestinal tract, leading to copper elimination.⁵

Copper plays a role as a cofactor for many enzymes, in electron-transportingproteins, and in antioxidant metabolism. The main copper-bindingprotein is ceruloplasmin which plays a role in copper transportand release and in protection of cells from oxidative damage.Both ferroxidase and ceruloplasmin may oxidize Fe²⁺ to Fe³⁺facilitating the release of Fe from ferritin and its bindingto transferrin.⁶ Copper is required for a variety of enzymes,including amino oxidase, ferroxidase, cytochrome-C-oxidase anddopamine hydroxylase. Copper is a cofactor for cytochrome oxidase,methallothionein and superoxide dismutase (SOD) involved inantioxidative responses.^6–8

The mechanism by which copper deficiency results in cytopeniasis not well understood. In general, many copper-containing proteinsare important for the proper function of the hematopoietic system.Copper deficiency decreases transferrin concentration in theplasma, and facilitates heme degradation secondary to an increasein heme oxygenase. Copper deficiency may result in a reductionin of cytochrome-C-oxidase, leading to a slower rate of electronflow and ATP production, and ultimately diminished hemoglobinsynthesis. Ceruloplasmin and copper-zinc SOD are decreased incopper deficiency, affecting the survival of erythrocytes.

This report was inspired by the clinical observation of 3 veryinformative cases of copper deficiency associated with cytopenia(Table 1).

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Table 1. Clinical characteristics of patients with cytopenias due to copper deficiency.

Patients and literature

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Patients and literature

Case 1
A 60-year-old woman presented with an unexplained 80 lb weightloss over 4 months. She complained of discomfort and numbnessin her fingertips and loss of sensation in her hands; she notedsimilar symptoms involving her lower extremities. She had graduallydeveloped progressive gait abnormalities and eventually becamewheelchair bound. Her past medical history included perniciousanemia, pancreatitis, and a cholecystectomy; there was no historyof alcohol abuse. The patient had been treated for perniciousanemia without response. Physical exam showed mild weaknessin both legs that was attributed to leg pain, reduced sensationto pain up to the anterior thighs bilaterally, and impairedvibratory sensation up to her knees. Proprioception was impairedin the feet and the ankles. Her gait was wide-based. MRI ofthe brain and spine were normal. Laboratory studies showed anormocytic anemia with hemoglobin as low as 86 g/L, reticulocytecount of 1.6%, WBC: 1.5x10⁹/L with absolute neutropenia (0.130x10⁹/L),and a normal serum vitamin B12 level, normal methylmalonic acidlevel, negative HTLV-I serology, and negative heavy metal screenincluding arsenic, mercury and lead. Initial and repeat bonemarrow biopsies were unremarkable with normal cellularity (Figure 1).Virtually no plasma cells were present in the aspirate smear.Based on the combination of the pancytopenia and the neurologicsigns and symptoms copper deficiency was suspected. Serum copperwas <2 ${propto}$ mol/L (normal: 13–24), ceruloplasmin level was20 mg/L (normal: 210–450), and 24 hr urine for copperwas 2 ug/24 hrs (normal 0–40). A diagnosis of copper deficiencywas made, and the patient was treated with 2 mg oral coppertwice daily; the dose was subsequently increased to 6 mg takenthree times a day. She showed an excellent hematologic responseapproximately 6 months after starting treatment. Neurologicalsymptoms stabilized with minimal improvement.

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Figure 1. Morphology of bone marrow in copper deficiency. (A) Bone marrow aspirate smears demonstrated multiple clear cytoplasmic vacuoles in promyelocytes (left panels) and proerythroblasts (right panels) from Case 1 (bottom panels) and Case 2 (top panels). Vacuolated cells were infrequent in both cases, and significant dysplastic features were not identified in either case. (Wright-Giemsa stain, original magnification 100x). (B) Bone marrow biopsy from Case 2 was slightly hypocellular for age (40%) with trilineage hematopoiesis, an erythroid predominance, and mild megakaryocytic hyperplasia. (H&E stain, original magnification 40x). (C) Hemosiderin (iron) containing plasma cells were noted in case 2. In the marrow aspirate approximately 25% of plasma cells contained cytoplasmic hemosiderin pigment (C1) that was highlighted in iron stain (C2). (H+E stain and pression stains, orginal magnification 100X).

Case 2
A 38-year-old woman who had a gastric bypass operation fouryears earlier presented for evaluation of unsuspected anemiafound when volunteering to become a blood donor. Upon furtherquestioning, the patient admitted to symptoms of fatigue formore than a month, lightheadedness and dizziness. She had numbnessin the distal part of her legs for a few months. She did nothave any other significant past medical history or any othersymptoms. Current medications included Mometasone Furoate, loratadine,zinc, calcium, prenatal vitamins, ester-CYP3A4, vitamin B12,vitamin B6, and ferrous sulfate. The physical examination wasunremarkable. A blood cell count showed WBC: 1.3x10⁹/L (normal:4.0–11.0), Hgb: 72 g/L (normal: 120–160), MCV 94.1fL (Normal: 80–100), and platelet count: 196x10⁹/L (normal150–400) (Table 1). There was severe neutropenia (0.240x10⁹/L).Ferritin, vitamin B12, folic acid, and TSH were within normallimits. Additional laboratory studies showed serum copper: <2 ${propto}$ mol/L (normal: 13–24) and serum zinc: <12.4 ${propto}$ mol/L (normal:8.4–22.9). Bone marrow aspirate and biopsy were slightlyhypocellular for age (40%) with trilineage hematopoiesis, anerythroid predominance, and mild megakaryocytic hyperplasia.Bone marrow aspirate smears demonstrated multiple clear cytoplasmicvacuoles in proerythroblasts, also plasma cells containing hemosiderinpigment were present (Figure 1). A diagnosis of copper deficiencywas established, and she was treated with oral copper 2 mg twicedaily. After 3 months a blood cell count showed: WBC: 7.55x10⁹/L,Hgb: 134 g/L, absolute neutrophil count: 4.27x10⁹/L and serumcopper: 17 ${propto}$ mol/L. Her neurologic symptoms completely resolved.

Case #3
A 53-year-old man presented with anemia, leukopenia and neurologicalsymptoms (Table 1). His symptoms started five years prior topresentation with numbness in his feet; this was followed byprogressive foot and hand weakness to the extent that he developedbilateral foot and wrist drop. His past medical history wassignificant for gastroesophageal reflux disease, frequent alcoholand tobacco use, and chronic normocytic anemia and leukopenia.Physical examination was negative except for bilateral weaknessin the wrists and feet, and reduced pinprick sensation fromtoes to ankles and from fingers to wrists; vibratory sensationwas absent at toes and ankles. Laboratory studies showed: WBC:2.32x10⁹/L (normal: 4.0–11), Hgb: 100 g/L (normal: 135–175),MCV: 99.3 fL (normal: 80–100), platelets: 197x10⁹/L (normal:150–400), and absolute neutrophil count: 1.72x10⁹/L. Additionalstudies showed serum zinc: 33.5 ${propto}$ mol/L (normal: 8.4–22.9),24 hr zinc excretion: 4,940 ug/24hr (normal: 150–1300),serum copper: <2 ${propto}$ mol/L (normal: 13–24), and serum ceruloplasmin:40 mg/L (normal: 21–45). He was treated with oral copper(2 mg twice daily which was increased to 5 mg twice daily untilthe present time. Five months later his blood cell count andcopper level normalized, but zinc level continued to be abovethe normal level.

Summary of previous cases
Systematic review of the literature from 1985 to 2005 was performedand identified 45 reported patients with severe copper deficiencyin addition to our three cases (Table 2). Of these, 47 (98%)had absolute neutropenia, 48 (100%) had anemia, and thrombocytopeniawas seen in 5 (10%). The anemia was microcytic in only 2 (4%)and macrocytic in 17 (35%). The serum copper level was low in47 (98%) patients. All patients were reported to be recoveredeither following copper supplementation or discontinuing zinc(if the copper deficiency was due to increased zinc ingestion).Twenty patients (41%) had documented neurological findings rangingfrom polyneuropathy, loss of sensation in the extremities, lossof vibratory sensation, sensory ataxia without involvement ofcerebellum, gait abnormalities with wide-based gait, increasedtone, weakness, exaggerated reflexes, loss of Babinski’sreflex and neurocognitive defects. Importantly, hematologicabnormalities due to copper deficiency were not always associatedwith neurologic symptoms. Available bone marrow findings revealedcytoplasmic vacuolization in 27 patients (56%), refractory anemiawith ringed sideroblasts (RARS) in 22/48 (41%), and 12/48 (25%)had a hypocellular bone marrow (Table 3).

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Table 2. Review of reported patients with pancytopenia and copper deficiency (1985 to 2005).

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Table 3. Review of MCV, ANC, platelet count and pathologic abnormalities in copper deficiency.

Discussion

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Discussion

The neurological symptoms of copper deficiency are well-defined.However, copper deficiency is only rarely recognized as a causeof pancytopenia. The causative relationship between decreasedcopper level and pancytopenia can be inferred from the excellentresponse to treatment with copper supplementation.

Our three well annotated cases of copper deficiency are veryillustrative and serve to highlight the main features that maytrigger targeted diagnostic tests to exclude copper deficiencyas a cause of cytopenias. Historically, 48 cases of copper deficiency,including three from our institution, were associated with hematologicabnormalities. The largest single series of published casesincluded ''10 patients.⁹ All reported cases of copper deficiencyshowed anemia and absolute neutropenia. MCV values were variable,and ranged from low to high. Thrombocytopenia was absent inmost cases, aside from patients receiving total parenteral nutrition.A rarely noted finding is the presence of prominent hemosiderinin plasma cells.²⁶ The majority of patients showed an improvementin their CBC or a complete hematologic response following eithertherapy with copper supplements or by eliminating excess dietaryzinc or zinc supplements.^10–12

Multiple reports have implicated low copper levels in the pathogenesisof selected cases of refractory anemia with ringed sideroblasts(RARS) responsive to copper; all cases had normal platelet counts.^13–15Refractory sideroblastic anemia was reported in 22 patients,and often occurred in association with excessive zinc ingestion,a finding causally linked to decreased copper levels. Stoppingzinc supplements or removing dietary sources of excess zincwas enough to achieve hematologic recovery in these patients.Less well characterized and more loosely associated were cytopeniaand myeloneuropathy are signs and symptoms of copper deficiencywere highlighted in several case reports.^1,2,16–20 Themost common causes of copper deficiency are malabsorption andmalnutrition, but as noted above, copper deficiency can alsooccur secondary to chronic use of large doses of zinc causingzinc overload syndrome.^21,22 Responsive to copper supplementationor zinc withdrawal in cases the diagnosis of RARS should beavoided, since the anemia is not refractory to treatment andtrue myelodysplastic syndrome is not present.

Chronic copper overdose, which is a very rare condition, maycause serious side effects including liver cirrhosis, episodesof hemolysis and kidney damage, and even death.

In conclusions our study demonstrates that copper and zinc levelsshould be checked in patients who present with cytopenias, especiallyin cases lacking thrombocytopenia, or having vacuolated erythroidprecursors in a marrow aspirate, or with increased RS. Copperdeficiency usually presents with bicytopenia (neutropenia andanemia), but severe pancytopenia has been observed in some cases,especially those patients on TPN. Hematologic recovery can beachieved with oral copper supplements administered for a fewweeks, but some patients may require supplementation using totalparenteral infusions. In cases of hyperzincemia or zinc overdose,discontinuing the zinc supplementation can be sufficient forhematologic recovery.

Footnotes

Supported in part by R01 655365071402, U54 – 655365070704,K24 655365071503, grant from the Aplastic Anemia and MDS InternationalFoundation NIH (to JPM).

References

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