Respiratory failure in spinal muscular atrophy: A case report and review of literature

V Vinay; Sushil Kumar Munjal; M N Dinesh Kanna; Sandeep Jain; Paras Verma; M Arunachalam

doi:10.4103/jopcs.jopcs_18_22

CASE REPORT

Year : 2023 | Volume : 4 | Issue : 1 | Page : 28-31

Respiratory failure in spinal muscular atrophy: A case report and review of literature

V Vinay¹, Sushil Kumar Munjal¹, M N Dinesh Kanna¹, Sandeep Jain¹, Paras Verma¹, M Arunachalam²
¹ Department of TB and Respiratory Diseases, National Institute of Tuberculosis and Respiratory Diseases, New Delhi, India
² Department of Pulmonary Medicine, Critical Care and Sleep Medicine, All India Institute of Medical Sciences, New Delhi, India

Date of Submission	11-Jul-2022
Date of Decision	19-Sep-2022
Date of Acceptance	10-Oct-2022
Date of Web Publication	16-Dec-2022

Correspondence Address:
Dr. V Vinay
Department of TB and Respiratory Diseases, Room No 29, 3^rd Floor, Doctors Quarters, National Institute of Tuberculosis and Respiratory Diseases, Sri Aurobindo Marg (Near Qutab Minar), New Delhi
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jopcs.jopcs_18_22

Abstract

Spinal muscular atrophy (SMA) type 2 is a neuromuscular disorder of childhood with high morbidity and mortality caused by the deletion of SMN1 gene (gene 1 of motor neuron survival), located at chromosome 5. It is the respiratory complications that account for the majority of deaths in SMA. This report describes an 18-year-old male patient diagnosed with SMA type 2, who had shortness of breath for 2 weeks and cough for 1 week. CT-Thorax revealed left lung collapse due to mucoid impaction in the left main bronchus. Bronchoscopy was challenging in this case due to severe kyphoscoliosis, and impacted mucus was extracted using bronchoscopy-guided forceps biopsy. Repeat X-ray of the chest following treatment showed no evidence of collapse, and patient was discharged in a stable condition with mucolytics and antibiotics.

Keywords: Autosomal recessive condition, bronchoscopic extraction, mucoid impaction, respiratory failure, spinal muscular atrophy

How to cite this article:
Vinay V, Munjal SK, Kanna M N, Jain S, Verma P, Arunachalam M. Respiratory failure in spinal muscular atrophy: A case report and review of literature. J Prim Care Spec 2023;4:28-31

How to cite this URL:
Vinay V, Munjal SK, Kanna M N, Jain S, Verma P, Arunachalam M. Respiratory failure in spinal muscular atrophy: A case report and review of literature. J Prim Care Spec [serial online] 2023 [cited 2023 Jun 6];4:28-31. Available from: https://www.jpcsonline.org/text.asp?2023/4/1/28/364031

Introduction

As an autosomal recessive disorder, spinal muscular atrophy (SMA) results in the degeneration and destruction of alpha motor neurons in the spinal cord and motor neuron nuclei in the lower brainstem. A homozygous deletion of SMN1 or SMN1 mutation causes a deficiency of the housekeeping protein "survival motor neuron" (SMN). This leads to muscle wasting, weakness, and feeding and respiratory difficulties. An estimated 1 in 6000–1 in 10,000 live births are affected by SMA, which has a carrier frequency of 1/40–1/60.^[1] The condition may lead to lung underdevelopment, decreased lung function, weak cough, and difficulty in clearing lung secretions, which increase the risk of pneumonia and hypoventilation. Mucoid impaction can be fatal, yet is a reversible cause of respiratory failure. Here, we report an uncommon case of SMA with respiratory failure that presented to us with the left lung collapse due to mucoid impaction.

Case Report

An 18-year-old young male came with complaints of shortness of breath for 2 weeks and cough for 1 week. He was diagnosed with SMA type II after birth and had a history of multiple hospitalizations for lower respiratory tract infections. A detailed history revealed that his brother is also suffering from the same illness with no history of consanguinity between the mother and father. On general physical examination, his heart rate was 120/min, blood pressure was 114/76 mmHg, respiratory rate was 30/min, and afebrile. Initial oxygen saturation on room air was 90% but improved to 97% on FiO₂ 28% through nasal prong at 2 L/min. On respiratory system examination, the trachea was shifted to the left side confirmed by palpation, with decreased movements of the left hemithorax and decreased tactile vocal fremitus on the left hemithorax. There was dullness on percussion of the left side of the chest in all areas. Air entry was decreased on the left hemithorax over all the areas. An examination of the right hemithorax revealed no abnormalities. Rest of the systemic examination was normal. The routine blood tests were within the normal limits. Possible differentials considered were aspiration pneumonitis, mucoid impaction, respiratory failure due to kyphoscoliosis and thoracic muscular atrophy, and community-acquired pneumonia.

Chest radiograph (PA view) showed left-sided homogeneous opacity [Figure 1]a. CT-Thorax delineated a hypodense material ~16 HU filling the left main bronchus causing collapse of the left lung with ipsilateral shift of mediastinum and heart [Figure 1]b, multilevel posterior and anterior arch anomalies and defects, with thoracic muscular atrophy and kyphoscoliosis was noted. The patient was started on empirical antibiotics and mucolytics (oral N-acetylcysteine and ambroxol nebulization). As there was no clinical and radiological improvement, bronchoscopy was planned. Bronchoscopy was quite challenging due to severe kyphoscoliosis, and it revealed mucus impacted in the left main bronchus [Figure 1]c. With the help of suction and biopsy forceps, mucus plug was extracted, and postextraction, respiratory distress was resolved [Figure 1]d. Bronchial wash from the lingula came positive for MRSA, for which linezolid was initiated. The patient was discharged in a stable condition with personalized therapy including manual chest percussion, antibiotics, mucolytics (short course), and annual influenza vaccination. Chest X-ray (PA view) after the treatment showed complete recovery from collapse [Figure 2].

Figure 1: Chest X-ray (PA view) showing homogenous opacity of the left hemithorax (a) and CT-Thorax (coronal view) showing collapse of the left lung with kyphoscoliosis (b). (c) Showing mucoid obstructing the left main bronchus. SMA patient with kyphoscoliosis and thoracic muscular atrophy postmucus extraction (d). SMA: Spinal muscular atrophy

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Figure 2: Chest X-ray (PA view) showing resolution of the left lung collapse postmucoid extraction and treatment with antibiotics

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Discussion

SMA is a fatal pediatric neuromuscular disorder with autosomal recessive inheritance.^[1] This disease is associated with a progressive symmetrical muscle weakness and atrophy caused by the loss of lower motor neurons (anterior horn cells) in the spinal cord and brainstem nuclei. There are five types of SMA, which are classified according to their clinical manifestations and their level of motor function [Table 1].^[2]

Table 1: Spinal muscular atrophy classification with characteristics and natural history^[2]

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The survival motor neuron 1 (SMN1) (5q13.2) gene mutations are responsible for causing homozygous loss of function.^[3] In most of the SMA cases (95%), patients have truncated nonfunctional SMN protein due to homozygous deletion of exon 7. Compounded heterozygous mutations, which include intragenic point mutations and exon 7 deletions, occur in a lesser proportion of cases. It is estimated that 10%–15% of the transcripts encoding SMN2 have exon 7, resulting in the full-length protein.^[4]

In the past, SMA has been treated with supportive care. There have been recent advances in disease-modifying agents that have become available. The approved disease-modifying agents aiming at increasing SMN protein expression, either by modulation of SMN2 splicing to increase exon 7 inclusion by inhibiting it or modulate exon 7 inclusion or gene therapy through systemic intravenous application of a nonreplicating self-complementary adeno-associated virus 9 that introduces SMN1 cDNA into the infected cell.^[3] Currently available disease-modifying agents are mentioned in [Table 2].^[5],[6],[7]

Table 2: Currently available disease-modifying agents

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The onset of respiratory failure and death is more likely to occur as a result of ineffective airway clearance due to respiratory muscle weakness and a weak cough. In pediatric airway, mucoid impaction with atelectasis is common due to the small caliber and insufficient collateral ventilation. Complications such as pneumonia, atelectasis, bronchiectasis, abscess formation, and respiratory failure can result from mucoid impactions.^[8] When mucoactive agents (hypertonic saline, N-acetylcysteine, dornase alfa, ambroxol, etc.) fail to clear mucus impaction either due to weak cough or respiratory muscle weakness, several bronchoscopic methods consisting of suction and forceps biopsy, Fogarty catheter,^[8] or bronchoscope-guided modified nasogastric suctioning^[9] can be tried, but rigid bronchoscopy and/or CryoProbe may be required to remove tenacious secretions that do not respond to suction or forceps.^[10]

An early intervention with the goal of improving airway clearance can reduce hospitalization and the incidence of complications. As a means of clearing the airway, preventing impaction, and improving quality of life, a variety of airway clearance techniques can be advised depending on the cough peak flow or whether the patient can sit or not. These include positioning, chest manipulations, manual chest physiotherapy, breathing exercises, positive expiratory pressure therapy, mechanical insufflator-exsufflator, and mucus mobilization devices (e.g.,: Afflo vest). Despite posing a significant risk of death, respiratory failure caused by mucoid impaction can be reversed if diagnosed early and treated on time. In our case, mucoactive agents failed to clear the impacted mucus due to a weak cough. Hence, it was removed using bronchoscope-guided suction and forceps biopsy. The management of cases like SMA should include individualized plans consisting of airway clearance, ventilation, nutrition, hydration, and antibiotics. Caretakers can use pulse oximetry to screen for lower airway complications of respiratory tract infections and to intensify airway clearance therapy when necessary.

Conclusion

SMA is a pediatric neuromuscular disorder with autosomal recessive inheritance caused due to mutation in the SMN-1 gene
The most common cause of mortality in SMA is respiratory infections
Multimodal interventions are necessary to improve nutritional status and bone health, to prevent muscular contractures, and to stabilize pulmonary function.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understand that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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