Over many years of pediatric practice, I have been impressed time and again with the difficulty in making an accurate diagnosis on a flaccid infant. I remember one infant previously diagnosed as having WerdnigHoffmann disease. The child was given a very poor prognosis by the examining pediatrician. She turned out to have a moderate case of cerebral palsy. Now, years later, she is doing very well in high school.
Another flaccid infant who did not sit up until 15 months of age proved to have benign hypotonia and developed into a normally active child.
In spite of such cases, it is important that an accurate diagnosis be made as soon as possible on a child with muscular weakness. In certain rare cases, such as in dermatomyositis, early treatment may be of help. But whether or not treatment is helpful, in all cases it is necessary that parents be directed on the care of the child and possibly given some hint as to the final prognosis. Also, one must determine if the condition is the result of a recessive gene - in which event genetic counseling would be of vital importance in considering future children.
Today, with our increasing knowledge of electromyography, muscle biopsy, muscle chemistry, and genetics, the diagnosis of the conditions causing muscular weakness has become much more definitive. In some institutions there is even a subspecialty of neurology devoted specifically to muscle diseases.
Some months ago, when we were discussing the publication of this issue of Pediatric Annals devoted to muscle diseases of infancy and childhood, it was suggested that we approach a specialist in this particular field to act as Guest Editor. Dr. Alfred J. Spiro was mentioned as an outstanding authority in this area. Dr. Spiro was contacted and accepted the editorship.
The finding of muscle weakness is not uncommon in the practice of pediatrics. Most of us have seen "floppy" infants and those who are slow in muscular development. We may see children in whom we suspect muscular dystrophy or some other weakening disorder. Usually we are unable to make a final diagnosis on the first examination and need corroborative evidence.
The steps to be followed in the investigation are the subject of the first article in this issue - "Approach to Diagnosis in the Child With Muscle Weakness." In this Dr. Spiro presents a "five-pronged" approach in arriving at a correct diagnosis. Each of the five categories he considers is discussed carefully and clearly. He warns firmly against diagnosing on symptoms alone. This is a valuable and basic article well worth reading by all pediatricians.
The second contribution to this symposium is by Dr. Niels L. Low and covers the "Spinal Muscular Atrophy Syndromes." These are conditions with muscular weakness characterized by absent or very weak tendon reflexes. They include such diseases as juvenile muscular atrophy, Werdnig-Hoffmann disease, and Kugelberg-Welander disease, and are due to a degeneration of the large anterior horn cells of the spinal cord. Practically all these cases are based on autosomal recessive inheritance, and the course is always downhill. Dr. Low also reviews the laboratory studies, heredity, and pathology related to these conditions.
This is followed by an article on the "Muscular Dystrophies of Childhood," by Drs. Gerald E. Slater and Kenneth F. Swaiman. This contribution is a very comprehensive study of the various types of dystrophy observed during childhood. Myopathies, which include dystrophies, are defined by Drs. Slater and Swaiman as primary diseases of striated muscle in which there are apparent biochemical, morphologic, or neuro physiologic changes.
The authors demonstrate clearly how definite diagnosis of dystrophy may be made by the study of serum enzyme activity, especially creatine Phosphokinase, pathology, and electromyography. The greatest attention is given to Duchenne's muscular dystrophy (pseudohypertrophic muscular dystrophy), the type most commonly seen in the practice of pediatrics.
Biochemistry, genetics, and present-day therapy are considered, as well as the numerous complications and behavioral and emotional abnormalities. The other forms of dystrophy described and discussed are late-onset X-linked muscular dystrophy, congenital muscular dystrophy, limb-girdle muscular dystrophy, facioscapulohumeral dystrophy, myotonic dystrophy, and some uncommon dystrophies.
This is an article worth saving for future reference when possible cases of muscular dystrophy occur in one's practice.
The fourth article is on the "Floppy Baby" and was written by Dr. Peggy A. Hanson. The author emphasizes a point made at the beginning of this review - namely, that one should not be too quick to make a diagnosis in this condition since some babies, even with striking abnormalities on muscle biopsy, progress to normalization. Dr. Hanson carefully enumerates the factors and abnormal conditions to be considered in the differential diagnosis. These include sepsis, meningitis, intracranial hemorrhage, cerebral hypoxia, inborn errors of metabolism, and congenital abnormalities. She also notes the neuromuscular diseases to be considered in studying the floppy infant. This is another excellent article of great value to the practicing pediatrician when faced by this difficult problem.
The final contribution, "Dermatomyositis of Childhood," is by Drs. Mary Elizabeth LeIl and Michael L. Swerdlow. Dermatomyositis is a comparatively rare disease in childhood causing muscle weakness. Its clinical picture is very impressive, with a typical rash accompanying the other symptoms. This has been a condition with high mortality, but since the advent of prednisone there has been considerable reduction in both mortality and severity of symptoms. For best results, however, treatment must be started early. Once again, the importance of the pediatrician in making a diagnosis is emphasized.
I am sure that this well-written, well-organized, and interesting issue of the magazine will prove of significant value to its readers.