Uncommonly Missed Diagnosis of Methylmalonic Acidemia (MMA) in Adults and Usefulness of Testing for MMA in Cases of Seizures/Neuropathy/Weakness/Ataxia

Methylmalonic acidemia (MMA) is a genetic condition affecting cobalamin metabolism causing elevated serum and urine methylmalonic acid without B12 deficiency. MMA presents with ketoacidotic hyperammonemic coma in newborns and can result in neonatal death or severe neurological disability. Rarely, this diagnosis is missed, or patients do not present until later in life. Presentation of this life-threatening condition is variable in adults. Improvement is rapid with IV cobalamin and a specialized diet. This case is intended to increase clinician's awareness of the late presentation of this disease and the importance of high clinical suspicion and prompt diagnosis. We present a case of a 32-year-old man with seizures, polyneuropathy, ataxia, and memory loss which were unexplained until diagnosis with MMA. We aim to help clinicians understand the variable presentation and diagnostic work-up of MMA to prevent catastrophic missed diagnoses. After an extensive work-up, the patient was found to have methylmalonic acidemia and was promptly treated with high dose vitamin B12 and a specialized diet with low protein including restricted isoleucine, threonine, methionine, and valines as well as a high caloric content. The patient showed significant clinical improvement with this treatment. To our knowledge, this is the first case of MMA presenting with these symptoms in a medically stable adult. The patient was adopted from abroad and therefore, lacked access to normal newborn screenings, further complicating diagnosis. We aim to demonstrate to clinicians the importance of considering this diagnosis in patients in whom symptoms may be suggestive, particularly if they lack access to genetic or metabolic screening.

Adult Refsum Disease in Puerto Rico: A Case Report

Patients with adult Refsum Disease (ARD) have retinitis pigmentosa and thus nyctalopia, anosmia, sensorineural deafness, polyneuropathy, and ataxia. Upon physical examination, patients with ARD have congenital short metacarpals, metatarsals, and cardiac arrhythmias. Manifestations due to the lack of phytanoyl-CoA hydroxylase in peroxisomes needed for alpha-oxidation of phytanic acid lead patients to accumulate phytanic acid in their body tissues. To our knowledge, no consensus for clinical diagnostic criteria for patients with ARD has been published. Our patient had nyctalopia, retinal findings, and visual field results compatible with retinitis pigmentosa. Additionally, the patient had decreased macular thickness and volume in both eyes, the findings being worse in the left eye. The patient had undergone hand surgery due to chronic pain in both hands, as well as his fourth and fifth metatarsal bones were shortened. Interestingly, audiology evaluation showed mild hearing loss in the right ear and mild to moderate hearing loss in the left ear. Inheritance patterns in patients with ARD have been described. Physical examination, phytanic acid evaluation, and genetic studies may all help reach an ARD diagnosis. This is the first report of adult Refsum disease in Puerto Rico.

Predictive Factors for Lower Limb Amputation in Type 2 Diabetics

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is a major public health problem. Foot-related complications are common in diabetic patients. The aim of this study is to identify predictive factors for lower limb amputation (LLA) in order to better identify this at-risk population.

METHODS

This was a cross-sectional study involving 134 patients who were hospitalised for the management of T2DM complicated by diabetic foot, in the department of endocrinology and diabetology. We included patients with T2DM whose diabetes was diagnosed 10 years ago or more, and who had a diabetic foot problem. Statistical differences between predictors of amputations were tested using: t-tests for numerical variables and chi-square tests for categorical variables. Significant variables were analysed by logistic regression to determine significant predictors.

RESULTS

The mean duration of diabetes was 17±7 years. We found that 70% of patients with LLA were older than 50 years (p<10-3). The prevalence of LLA was higher (p=0.015) in patients with diabetes for more than 20 years. We noted that 58% of patients who underwent LLA were hypertensive (p<10-3). The majority of patients with LLA (58%) had abnormal micro-albuminuria (p<10-3). We found that 70% (n=12) of patients with LLA had low-density protein cholesterol levels above the target value (p<10^-3). Diabetic foot grade ≥4 (4 or 5) according to Wagner's classification, was present in 24% of amputee patients. Based on a 95% confidence interval level, the independent significant predictive factors for LLA in our patients were: T2DM for more than 20 years, hypertension and diabetic foot grade ≥4.

CONCLUSIONS

After multivariate analysis, the significant independent predictive factors associated with LLA were: T2DM for more than 20 years, hypertension, and diabetic foot grade ≥4. Early management of diabetic foot problems is therefore recommended to avoid amputations.

Small Fiber Neuropathy Associated With the Moderna SARS-CoV-2 Vaccine

Efforts of controlling viral transmission began soon after the first cases of coronavirus disease 2019 (COVID-19) infections were identified. Initial efforts were related to contact precautions, hand hygiene, and mask-wearing; however, it was soon evident that a robust global immunization drive was the most effective way to curb disease transmission. In the United States, the first doses of COVID-19 vaccines were rolled out soon after the FDA granted emergency use authorization for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. What this also meant was that many of the routine phases that any new drug or vaccine goes through before being released publicly were bypassed. Over the past two years, various side effects and reactions have been seen after COVID-19 vaccine administration, the most common being local injection site events (e.g., pain, redness, swelling) and systemic effects (e.g., fatigue, headaches, myalgias). We report the case of a 64-year-old female who developed bilateral lower extremity numbness and tingling within weeks of receiving the third dose of Moderna SARS-CoV-2 vaccine. The patient underwent extensive testing to ascertain the diagnosis. She had negative autonomic testing and normal nerve conduction study/electromyography (EMG), which did not reveal large fiber neuropathy. Eventually, the patient underwent a skin biopsy, which revealed small fiber neuropathy. This case report highlights the importance of keeping a broad differential for rare side effects, such as small fiber neuropathy, that are currently being seen and reported in the literature.

Nanoparticle albumin-bound paclitaxel is superior to liposomal paclitaxel in the neoadjuvant treatment of breast cancer

Aim: The present study aimed to retrospectively compare the efficacy and safety between liposomal paclitaxel (Lps-P) and nanoparticle albumin-bound paclitaxel (Nab-P) in neoadjuvant systemic treatment (NST) of breast cancer. Materials & methods: 235 patients who were diagnosed with invasive breast cancer and then received dose-dense NST with epirubicin and cyclophosphamide followed by paclitaxel were enrolled. Results: Nab-P has an advantage in improving the total and axillary-only pathologic complete response rate over Lps-P. Although Nab-P can cause a higher incidence and severity of peripheral sensory neuropathy (PSN), most symptoms are temporary and reversible. In the Lps-P group, the proportion of patients with residual irreversible PSN is larger. Conclusion: Nab-P might be superior to Lps-P in NST of breast cancer.

Large-Scale Prospective Genome-Wide Association Study of Oxaliplatin in Stage II/III Colon Cancer and Neuropathy

IMPORTANCE

The severity of oxaliplatin (L-OHP)-induced peripheral sensory neuropathy (PSN) exhibits substantial interpatient variability, and some patients suffer from long-term, persisting PSN.

OBJECTIVE

To identify single-nucleotide polymorphisms (SNPs) predicting L-OHP-induced PSN using a genome-wide association study (GWAS) approach.

DESIGN, SETTING, PARTICIPANTS

A large prospective GWAS including 1,379 patients with stage II/III colon cancer who received L-OHP-based adjuvant chemotherapy (mFOLFOX6/CAPOX) under the phase II (JOIN/JFMC41) or the phase III (ACHIVE/JFMC47) trial.

MAIN OUTCOMES AND MEASURES

First, GWAS comparison of worst grade PSN (grade 0/1 vs. 2/3) was performed. Next, to minimize the impact of ambiguity in PSN grading, extreme PSN phenotypes were selected and analyzed by GWAS. SNPs that could predict time to recovery from PSN were also evaluated. In addition, SNPs associated with L-OHP-induced allergic reactions (AR) and time to disease recurrence were explored.

RESULTS

No SNPs exceeded the genome-wide significance (p < 5.0 × 10^-8) in either GWAS comparison of worst grade PSN, extreme PSN phenotypes, or time to recovery from PSN. Association study focusing on AR or time to disease recurrence also failed to reveal any significant SNPs.

CONCLUSION AND RELEVANCE

Our results highlight the challenges of utilizing SNPs for predicting susceptibility to L-OHP-induced PSN in daily clinical practice.

Efficacy and safety of modified fluorouracil/leucovorin plus irinotecan and oxaliplatin (mFOLFIRINOX) compared with S-1 as second-line chemotherapy in metastatic pancreatic cancer

BACKGROUND AND AIM

The optimal standard second-line chemotherapy for metastatic pancreatic cancer (MPC) remains unclear. Here, we evaluated the efficacy and safety of modified fluorouracil/leucovorin plus irinotecan and oxaliplatin (mFOLFIRINOX) compared with oral fluoropyrimidine S-1 as a second-line chemotherapy in patients with MPC.

METHODS

We retrospectively reviewed 76 consecutive patients with metastatic pancreatic adenocarcinoma who underwent mFOLFIRINOX or S-1 treatment as a second-line chemotherapy after gemcitabine plus nab-paclitaxel (GnP) failure at our department between December 2014 and February 2019.

RESULTS

Patients who underwent mFOLFIRINOX treatment exhibited significantly better objective response rates (ORRs) and progression-free survival (PFS) than S-1 (ORR, 20.0% vs 0%, P = 0.003; PFS, 3.7 vs 2.1 months, P = 0.010). Although baseline patient characteristics of age, performance status, and serum albumin levels differed significantly between the two groups, mFOLFIRINOX was identified as an independent factor of favorable PFS on multivariate analyses. Grade 3-4 neutropenia and peripheral sensory neuropathy occurred more frequently in the mFOLFIRINOX group. The median overall survival from the initiation of second-line chemotherapy was not significantly longer in the mFOLFIRINOX group than in the S1 group (8.5 vs 5.8 months, respectively; P = 0.213); however, the 8-month survival rate was significantly higher in the mFOLFIRINOX group (56.0% vs 27.5%, respectively; P = 0.030).

CONCLUSIONS

mFOLFIRINOX as a second-line regimen contributed to favorable treatment outcomes, but induced more frequent adverse events than S-1. On multivariate analyses, mFOLFIRINOX was identified as an independent factor with favorable PFS, suggesting that mFOLFIRINOX could be a promising treatment option for patients with GnP failure.

Relative Risk of Peripheral Neuropathy With Ado-Trastuzumab Emtansine (T-DM1) Compared to Taxane-Based Regimens in Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Cancers: A Systematic Review and Meta-Analysis

Background

Peripheral neuropathy (PN), especially peripheral sensory neuropathy (PSN), is significant toxicity of taxanes, the most used class of microtubule inhibitors for human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients. Ado-trastuzumab emtansine (T-DM1) is a HER2-targeted antibody-drug conjugate, consisting of trastuzumab and a microtubule inhibitor DM1, which has been approved for HER2-positive breast cancer. T-DM1 has also been found to cause significant PN, including PSN.

Methods

We conducted a systematic review and meta-analysis of phase 3 randomized controlled trials using T-DM1 in the experimental arm and a taxane-based regimen in the control arm to determine the relative risk of PN and PSN associated with T-DM1 as compared to taxanes. A total of 1,857 patients were included in the analysis. The Cochran-Mantel-Haenszel method and the random-effects model were used to calculate the pooled risk ratio (RR) with a 95% confidence interval (CI) for all-grade and grade ≥3 PN and PSN. 

Results

The relative risks of all-grade PN and all-grade PSN were lower with T-DM1 compared to taxanes. The pooled RR of all-grade PN was 0.59, 95% CI: 0.39-0.89, P = 0.01, and the pooled RR of all-grade PSN was 0.58, 95% CI: 0.46-0.74, P < 0.0001.

Conclusions

Our meta-analysis demonstrated that T-DM1 is associated with a relatively lower risk of all-grade PN and PSN than the taxane-based regimens for HER2-positive cancers. It could be an area of consideration in selecting therapy for HER2-positive breast cancer patients at high risk of developing or having pre-existing PN and PSN.

Is nab-paclitaxel better than conventional taxanes as neoadjuvant therapy for breast cancer? A meta-analysis

Objective

This study compared the efficacy and safety of nanoparticle albumin-bound paclitaxel (nab-paclitaxel) with conventional taxanes as neoadjuvant chemotherapy for breast cancer.

Methods

We searched the literature using PubMed, the Cochrane Library, and Web of Science from their inception to December 15, 2019 based on predetermined inclusion and exclusion criteria. The relevant studies compared pathologic complete response (pCR) and adverse event rates.

Results

The meta-analysis included five studies and 2335 patients. Compared with conventional taxanes, neoadjuvant chemotherapy with nab-paclitaxel was associated with a higher pCR rate (odds ratio [OR] = 1.39, 95% confidence interval [CI] = 1.16–1.67), especially among patients with triple-negative breast cancer or Ki67 indices of >20%. Pooled outcomes also revealed better event-free survival in the nab-paclitaxel group (hazard ratio = 0.69, 95% CI = 0.57–0.85). However, all-grade (OR = 2.17, 95% CI = 1.38–3.40) and grade ≥3 peripheral sensory neuropathy (OR = 3.92, 95% CI = 2.44–6.28) were more frequent in the nab-paclitaxel group.

Conclusions

This meta-analysis implied that nab-paclitaxel more effectively improved pCR than conventional taxanes. Nab-paclitaxel may have greater benefits in patients with triple-negative breast cancer. However, additional attention is required for the early diagnosis and management of peripheral sensory neuropathy.

Peripheral and Autonomic Neuropathy Status of Young Patients With Type 1 Diabetes Mellitus at the Time of Transition From Pediatric Care to Adult-Oriented Diabetes Care

INTRODUCTION

The prevalence of neuropathic lesions in young patients with type 1 diabetes mellitus (T1DM) at the time of transition from pediatric care to adult-oriented diabetes care is poorly studied. A comparative study with healthy volunteers to assess the possible neuropathic condition of this special population and to identify the potential early screening needs has not been performed yet. The results may provide important feedback to pediatric diabetes care and a remarkable baseline reference point for further follow up in adult diabetes care.

PATIENTS AND METHODS

Twenty-nine young patients with T1DM [age: 22.4 ± 2.9 years; HbA1c: 8.5 ± 2.1%, diabetes duration: 12.2 ± 5.8 years; (mean ± SD)] and 30 healthy volunteers (age: 21.5 ± 1.6 years; HbA1c: 5.3 ± 0.3%) were involved in the study. Autonomic function was assessed by standard cardiovascular reflex tests. Complex peripheral neuropathic testing was performed by Neurometer^®, Neuropad^®-test, Tiptherm^®, Monofilament^®, and Rydel-Seiffer tuning fork tests.

RESULTS

T1DM patients had significantly higher diastolic blood pressure than controls (80 ± 9 vs. 74 ± 8 mmHg, p < 0.01), but there was no significant difference in systolic blood pressure (127 ± 26 vs. 121 ± 13 mmHg). Cardiovascular reflex tests had not revealed any significant differences between the T1DM patients and controls. No significant differences with Neurometer^®, Neuropad^®-test, and Monofilament^® were detected between the two groups. The vibrational sensing on the radius on both sides was significantly impaired in the T1DM group compared to the controls with Rydel-Seiffer tuning fork test (right: 7.5 ± 1.0 vs. 7.9 ± 0.3; left: 7.5 ± 0.9 vs. 7.9 ± 0.3, p < 0.05). The Tiptherm^®-test also identified a significant impairment in T1DM patients (11 sensing failures vs. 1, p < 0.001). In addition, the neuropathic complaints were significantly more frequently present in the T1DM patient group than in the controls (9 vs. 0, p < 0.01).

CONCLUSION

In this young T1DM population, cardiovascular autonomic neuropathy and cardiac morphological alterations could not be found. However, Rydel-Seiffer tuning fork and Tiptherm^®-tests revealed peripheral sensory neurological impairments in young T1DM patients at the time of their transition to adult diabetes care.

Charcot-Marie-Tooth Type 2B: A New Phenotype Associated with a Novel RAB7A Mutation and Inhibited EGFR Degradation

The rare autosomal dominant Charcot-Marie-Tooth type 2B (CMT2B) is associated with mutations in the RAB7A gene, involved in the late endocytic pathway. CMT2B is characterized by predominant sensory loss, ulceromutilating features, with lesser-to-absent motor deficits. We characterized clinically and genetically a family harboring a novel pathogenic RAB7A variant and performed structural and functional analysis of the mutant protein. A 39-year-old woman presented with early-onset walking difficulties, progressive distal muscle wasting and weakness in lower limbs and only mild sensory signs. Electrophysiology demonstrated an axonal sensorimotor neuropathy. Nerve biopsy showed a chronic axonal neuropathy with moderate loss of all caliber myelinated fibers. Next-generation sequencing (NGS) technology revealed in the proband and in her similarly affected father the novel c.377A>G (p.K126R) heterozygous variant predicted to be deleterious. The mutation affects the biochemical properties of RAB7 GTPase, causes altered interaction with peripherin, and inhibition of neurite outgrowth, as for previously reported CMT2B mutants. However, it also shows differences, particularly in the epidermal growth factor receptor degradation process. Altogether, our findings indicate that this RAB7A variant is pathogenic and widens the phenotypic spectrum of CMT2B to include predominantly motor CMT2. Alteration of the receptor degradation process might explain the different clinical presentations in this family.

Vibrotactile sensitivity of patients with HIV-related sensory neuropathy: An exploratory study

BACKGROUND

HIV-associated distal polyneuropathy (HIV-PN) affects large and small sensory nerve fibers and can cause tactile insensitivity. This exploratory study forms part of an effort to apply subsensory electrical nerve stimulation (SENS) to improve tactile sensitivity of patients with HIV-PN. This work presented an opportunity to use a robust protocol to quantitatively describe the vibrotactile sensitivity of individuals with HIV-PN on effective antiretroviral therapy (ART) and correlate these findings with commonly used clinical vibration testing and scoring grades.

METHODS

The vibration perception thresholds (VPTs) of 20 patients with HIV-PN at three vibration frequencies (25, 50, and 128 Hz) were measured. We compare the vibration perception threshold (VPT) outcomes to an age- and gender-matched control cohort. We further correlated VPT findings with 128 Hz tuning fork (TF) assessments performed on the HIV-PN participants, accrued as part of a larger study. HIV-PN was defined as having at least one distal symmetrical neuropathic sign, although 18 of 20 had at least two neuropathic signs.

CONCLUSIONS

HIV-PN participants were found to have lower VPT sensitivity than controls for all three vibration frequencies, and VPT was more sensitive at higher vibration frequencies for both HIV-PN and controls. VPT sensitivity was reduced with older age. Years on ART was correlated with VPT-25 Hz but not with VPT in general. Notably, VPT sensitivity did not correlate with the clinically used 128 Hz TF severity grades. Outcomes of tests for interaction with vibration frequency suggest that HIV-PN pathology does not affect all mechanoreceptors similarly.

Charcot Marie Tooth 2B Peripheral Sensory Neuropathy: How Rab7 Mutations Impact NGF Signaling?

Charcot-Marie-Tooth 2B peripheral sensory neuropathy (CMT2B) is a debilitating autosomal dominant hereditary sensory neuropathy. Patients with this disease lose pain sensation and frequently need amputation. Axonal dysfunction and degeneration of peripheral sensory neurons is a major clinical manifestation of CMT2B. However, the cellular and molecular pathogenic mechanisms remain undefined. CMT2B is caused by missense point mutations (L129F, K157N, N161T/I, V162M) in Rab7 GTPase. Strong evidence suggests that the Rab7 mutation(s) enhances the cellular levels of activated Rab7 proteins, thus resulting in increased lysosomal activity and autophagy. As a consequence, trafficking and signaling of neurotrophic factors such as nerve growth factor (NGF) in the long axons of peripheral sensory neurons are particularly vulnerable to premature degradation. A “gain of toxicity” model has, thus, been proposed based on these observations. However, studies of fly photo-sensory neurons indicate that the Rab7 mutation(s) causes a “loss of function”, resulting in haploinsufficiency. In the review, we summarize experimental evidence for both hypotheses. We argue that better models (rodent animals and human neurons) of CMT2B are needed to precisely define the disease mechanisms.