Patient 1 is a 29-year-old Iranian-Jewish woman diagnosed at age 24 years. She presented at age 17 with inability to abduct her legs against any resistance on an exercise machine; other muscle groups were strong. Following her first pregnancy at age 20, she noticed weakness, difficulty climbing stairs, and tripping and falling that progressed in frequency over the next 3 years from once a month to once a week. A muscle biopsy and genetic testing confirmed the diagnosis of HIBM with homozygous M712T mutations in GNE. At age 25, she noted difficulty fastening snaps and could not raise her arms to pull back her hair. Progression was gradual, with more significant decline following illnesses. Treatments included solumederol, 1 g intravenously for 3 days, which resulted in improved strength but was followed by relapse. On one occasion, IVIG (dose unknown) was given over 3 days, providing no improvement but complicated by aseptic meningitis requiring hospitalization. For the 6 months prior to admission, the patient used a wheelchair and required assistance walking and with transfers. Medications included sertraline for depression and anxiety, and vitamins.
At the NIH Clinical Center, the patient was wheelchair dependent, but could go from sit to stand and ambulate a few feet with support. She had bilateral foot drop and significant weakness of upper and lower extremities, with some sparing of the quadriceps. Muscle atrophy was universally apparent. Cranial nerves and sensation were intact. MRI of the calf showed pronounced fatty involution of the musculature bilaterally, worse proximally. The lateral soleus and posterior tibial muscles were somewhat spared distally. A quadriceps muscle biopsy revealed moderate type II fiber predominance. The muscles were atrophic (type II worse than type I) and demonstrated necrosis, active degeneration, and red rimmed vacuoles, consistent with severe chronic myopathy without inflammation. Imunohistochemical staining for NCAM, a surface glycoprotein reflecting muscle regeneration [23
], showed a significant number of positive fibers.
Patient 2 is the 42-year-old brother of patient 1. He was diagnosed with HIBM at 37 years of age, following the diagnosis of his sister. Weakness upon raising his arms overhead first appeared at age 27. At 34, he began tripping and, in the subsequent year, had difficulty climbing stairs and lifting his son. The upper extremities were most affected, but leg weakness was evident by decreased endurance, speed of walking, and getting in and out of a car. He occasionally used his hands to lift his legs. Symptoms were largely stable, but exacerbated by emotional events. He did not receive any treatment for his myopathy, and medications included only multivitamins.
At the NIH Clinical Center, there was wasting of the triceps and the interosseus and thenar muscles of the hand. Contractures of approximately 5–10 degrees were present in the elbows, with decreased range of motion upon supination of the forearm. The patient had no foot drop. Muscles of the shoulder girdle, pinch, grip, and proximal lower extremities exhibited weakness. The gait was normal, and cranial nerves and sensation were intact. MRI of the thigh revealed advanced atrophy with fatty involution in the proximal posterior compartment and adductor magnus muscles bilaterally. The sartorius and rectus femoris muscles were also involved. There was relative sparing of the quadriceps with the exception of the rectus femoris muscles. On biopsy, the quadriceps muscle showed several small vacuolated fibers with a few degenerating fibers, but no inflammation. Immunohistochemical staining was negative for NCAM, indicating negligible damage to individual muscle fibers.
Patient 3 is a 39-year-old woman of Bohemian/Czech/French Canadian ancestry diagnosed with HIBM at the age of 31 years. Following a year of progressive tripping and falling, she awoke one day with numbness from the waist down that spread to her entire body. She was diagnosed with mild multiple sclerosis, based on the presence of oligoclonal bands in her cerebrospinal fluid and a brain MRI showing a possible "spot." Muscle biopsy also provided evidence of inclusion body myopathy. Currently, she has difficulty arising from a supine position due to weak abdominal muscles, weakness in her hands, arms, and shoulders, and inability to climb stairs. She wears ankle braces to walk. She uses bronchodilators for asthma and sertraline for depression. Confirmatory mutational analysis demonstrated compound heterozygous GNE mutations, i.e., R246Q and A631V, affecting the epimerase and kinase domains, respectively.
At the NIH Clinical Center, the patient had bilateral foot drop with a compensated gait. She was able to transfer independently from sit to stand and from stand to sit. There was proximal muscle and neck weakness and limited endurance. Cranial nerves and sensation were intact. MRI of the calf showed end-stage myopathy with advanced fatty involution, but with preservation of muscle volume. Signal alteration was present in areas of non-atrophic muscle. The popliteal muscles in the upper calves and the distal posterior tibial muscles were relatively spared. On biopsy, the quadriceps muscle showed significant necrosis with replacement of muscle by fat and connective tissue, but without inflammation. NCAM staining was minimal.
Patient 4 is the 46-year-old brother of patient 3. He was diagnosed with HIBM at the age of 33 years following a one-year history of progressive tripping and falling, decreased muscle strength and inability to lift his foot. As a cabinetmaker, he relied on this action to support the cabinets as he made them. A muscle biopsy was initially read as consistent with either polymyositis or inclusion body myopathy, but intravenous steroids provided no relief, and HIBM was diagnosed. Plateaus were interspersed with declines, which occurred with lack of exercise but not with illnesses. The lower extremity weakness extended throughout the body. The patient currently wears ankle braces to walk, uses an electric wheelchair for distances, and has assistive devices to drive. He has difficulty holding a pen. Medications include acyclovir, Metamucil, multivitamins, tramadol and diazepam.
At the NIH Clinical Center, there was muscle wasting of the triceps and the interosseus muscles of the hands, along with tightness of the heel cords, hips, and hamstrings. The patient was partially independent when going from sit to stand, and when executing transfers to and from his wheelchair. He could ambulate a few steps using ankle-foot orthotics and support from the wall. He had significant weakness in the proximal upper extremities, triceps, wrist and hand, and decreased strength on hip flexion, hip extension, ankle dorsiflexion, and plantar flexion. Deep tendon reflexes could not be elicited in the upper or lower extremities. Sensation and cranial nerve functions were intact. MRI of the calf showed end-stage myopathy with advanced fatty involution but preservation of muscle contours. Signal alteration occurred in areas of the remaining muscle. There was relative sparing of the popliteus, the tibialis posterior, and the flexor digitorum longus muscles. Quadriceps muscle histology revealed vacuolated and moth-eaten muscle fibers, with degeneration and regeneration. Connective tissue was slightly increased with no signs of inflammation. Immunohistochemical staining with NCAM was negative.
Effects of IVIG on serum IgG
IgG levels during the course of the study are shown in Figure . The loading doses of IVIG brought the serum IgG levels to approximately 4 times the baseline, but this concentration of IgG was not sustained by the weekly infusions of 400 mg/kg of IVIG. Throughout the course of the infusion, the patients' serum IgG concentrations ranged from 2 to 4 times the average normal level.
Serum IgG levels in patients during the course of treatment with IVIG. Arrows indicate loading doses (1 g/kg) and maintenance doses (0.4 g/kg).
On quantitative muscle testing, both distal and proximal muscle groups showed improvement after IVIG treatment. The greatest absolute improvement was in quadriceps strength, as reflected in the capacity to perform work in knee extension. Considering both sides of all 4 patients, mean quadriceps strength improved from 19.0 kg at baseline, to 23.2 kg (+22%) directly after IVIG loading, to 25.6 kg (+35%) at the end of the study. Considered individually, the 4 patients exhibited a 13–150% improvement in the dominant right leg after IVIG treatment (Figure ). The change in left leg quadriceps strength varied from -3% to +48%. Shoulder abduction also showed significant improvement. Considering both sides of all 4 patients, mean shoulder strength improved from 4.1 kg at baseline, to 5.9 kg (+44%) directly after IVIG loading, to 6.0 kg (+46%) at the end of the study. Considering each patient individually, shoulder abduction on the right side improved 24–79% in three patients and fell 14% in patient 3 (Figure ). On the left side, shoulder abduction improved 13–184%.
Figure 2 Quadriceps and shoulder abduction testing in four patients with HIBM. On average, quadriceps strength increased 22% after IVIG loading and 35% at the end of the study. Shoulder abduction strength increased 44% after IVIG loading and 46% at the end of (more ...)
Eight other muscle pairs (right and left), associated with hip flexion, ankle dorsiflexion, elbow flexion and extension, wrist flexion and extension, grip, and pinch, were also evaluated. These muscle groups exhibited variable differences in strength before and after IVIG treatment (Table ), but the preponderance showed improvement. In fact, on average, the composite improvement for these 8 muscle groups was 5% after the initial IVIG loading and 19% by the end of the study. Tongue strength, which is not known to be affected in HIBM, improved ~5%, from a mean of 63.1 kp at baseline to a mean of 66.2 kp at the end of the study.
Strength of muscle groups of 4 HIBM patients at baseline and after IVIG treatment.
Functional studies included functional reach, timed up and go, and the 6-min walk test. Patient 1 could not perform any of these tests. Patient 4 could not perform the 6-min walk test.
In patient 2, the functional reach after IVIG treatment increased from 7.3 in to 10.2 in (40%) on the right and from 6.0 in to 8.8 in (47%) on the left. However, the functional reach declined in patients 3 and 4 by 8% and 19%, respectively. The time it took to rise from a chair (timed up and go) improved 1.94 s (27%) for patient 2 and 0.81 s (8%) for patient 3; it worsened by 0.84 s (5%) in patient 4. Endurance, as measured by the 6-min walk test, improved after IVIG treatment from 1633 ft to 1744 ft (7%) in patient 2 (normal mean for age and size, 1997 ft) and from 983 ft to 1065 ft (8%) in patient 3 (normal mean, 1637 ft).
Improvements in the two patients with abnormal modified barium swallows were also noted. Patient 1 had normal esophageal peristalsis with only mild delays after IVIG and patient 3 had no reflux or pooling with only delayed initiation after the treatment.
Patients displayed qualitative or subjective improvements as well. Patient 1 claimed improved strength, energy, and balance and needed less support to walk. She could get in and out of a bed or chair more easily. Brushing her hair was easier. She was able to open a bottle of water and cut a bagel without help. After IVIG treatment, she could snap her fingers and produce noise, which she had been unable to do for years. Patient 2 noted improvements in getting out of bed or a car. He could easily wash his hands and face, which was a struggle before treatment. He could reach further and could lift his children; he had more energy to play with them. Both he and his wife noticed that he walked faster. Patient 3 noted improvements with getting out of bed and up from a sitting position. She needed less support to accomplish her activities of daily living and appreciated increased energy. Patient 4 stated that he felt better, but was unable to provide specific examples. The subjective improvements lasted approximately three weeks, after which each of the patients noted a decline in function.
Serum transferrin contains four terminal sialic acid residues on its N-linked oligosaccharides [36
]. On isoelectric focusing, all four oligosaccharides were sialylated in all four patients before IVIG treatment, just after loading, and at the end of the treatment period [see Additional file 1
]. Similarly, the O-linked serum glycoprotein Apo C-III [37
] exhibited a normal contingent of sialylation in all four patients before and after IVIG treatment [see Additional file 1
Muscle MRI examinations were not repeated after IVIG treatment, because one month was not deemed a sufficient amount of time to achieve visible improvement. Standard histology of muscle biopsies showed no difference before compared with after IVIG treatment. The post-treatment biopsy of patient #3 was unsuitable for interpretation, but muscle biopsies from patients 1, 2, and 4 before and after IVIG treatment were available for staining with anti-α-dystroglycan antibodies (VIA4I and IIH6). No consistent differences were seen before and after treatment (Figure ). Immunoblotting showed no consistent increase in the glycosylation status of α-dystroglycan (using the IIH6 antibody) after IVIG treatment (Figure ).
Figure 3 Expression of α-dystroglycan in quadriceps muscle from HIBM patients. A-F. Immunohistochemistry using antibodies to IIH6. No consistent difference in staining was apparent before (A,C,E) compared with after (B,D,F) IVIG treatment. The specimen (more ...)
NCAM is a sialylated glycoprotein that plays a significant role in muscle fiber development, innervation and regeneration, and whose abundance on the surface of muscle cells reflects the extent of muscle denervation or damage [23
]. Patient 1 exhibited the greatest amount of muscle NCAM before IVIG (Figure ), i.e., 4-fold that of the N1
(normal) control, relative to actin, as determined by densitometry. After IVIG treatment, the muscle NCAM of patient 1 decreased by 34%. The amount of NCAM decreased by 28% in patient 2, but increased by 58% in patient 4, relative to actin after IVIG administration. In all cases, the HIBM patients' NCAM bands ran lower than the control, reflecting a decreased sialic acid content of this glycoprotein. This was verified for patient 2 by using sialidase to remove terminal sialic acid residues (Figure ). Sialidase treatment resulted in greater mobility of the normal muscle NCAM protein, but not that of patient 2 (Figure ). Sialidase treatment did, however, reduce the apparent size of muscle NCAM in patient 1, indicating the presence of some sialylation.
Figure 4 Expression of sialylated NCAM in muscle of HIBM patients. A. Muscle from two control individuals exhibit NCAM mobility consistent with a higher molecular weight, indicative of sialylation. N1 is normal and N2 has sporadic IBM; note increased NCAM in this (more ...)
NCAM immunohistochemical staining of HIBM muscle (patient 1, 2, and 4) after IVIG treatment did not reveal any consistent differences compared with pre-treatment staining (data not shown).
All patients experienced fatigue and headache following the second loading dose of 1 g/kg IVIG. Patients 1, 2, and 3 had several episodes of nausea and vomiting; patient 2 said it resembled having influenza. Patient 4 had headache and neck stiffness. Patients 1 and 2 experienced anorexia, and patient 2 had abdominal distension and constipation. The headaches were treated with naproxen or acetaminophen. Patient 3 required zofran for relief of the nausea and vomiting. All symptoms resolved by 72 h and did not recur with subsequent maintenance infusions of IVIG. A urinary tract infection was diagnosed incidentally in patient 1, and was treated. The follow-up ophthalmologic evaluation in patient 4 revealed a cottonwool spot near the left optic disc.
Patients 3 and 4 responded to the IVIG with increased sedimentation rates, as high as 96 mm/h (Table ). Liver enzymes rose slightly in patients 1, 2 and 4; the highest levels were obtained in patient 2, with an ALT of 81 U/L and an AST of 68 U/L. These values subsequently returned to normal. Serum cholesterol levels generally fell, from a mean of 200 mg/dL at baseline to 147 mg/dL just after loading and 173 mg/dL at the end of the study. Remarkably, the four patients excreted 6.4 to 30.8 g/d of glucose in their urine just after the IVIG load, compared with ≤0.1 g/day before and after the study. There were no significant changes in serum electrolytes, glucose, calcium, phosphorus, or bilirubin.
Laboratory values at baseline, after loading with IVIG (1 g/kg × 2), and at the end of IVIG treatment.