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[Distal myopathies: clinical, laboratory, electromyographic, histologic-histochemical analysis of 8 cases]
L C Werneck1, C D Marrone, R H Scola
1Serviço de Doenças Neuromusculares, Hospital de Clínicas, Universidade Federal do Paraná (UFPR), Brasil.
Abstract:
Distal myopathies are uncommon diseases presenting difficulties in the classification by the lack of sufficient knowledge on pathogenesis. We describe eight cases of distal myopathies (five male and three female patients) whose symptoms started at the age of 10 in five and 20 in three. Symptoms started in the distal muscles of lower limbs, following decreased strength in the distal portion of upper limbs, and later on involvement of proximal muscles. Serum enzymes increase was slight in five, moderate in one, and important in two. EMG suggested primary myopathy in four, denervation in two, and was mixed type in another. Muscle biopsies showed features of myopathy and denervation in two cases, active chronic myopathy in five, and chronic myopathy in another. Four cases had vacuoles with positive acid phosphatase reaction and in two cases rimmed vacuoles were found. Six cases had increase of focal phosphatase acid in the muscle fibers suggesting a lissome participation in the pathogenesis of the disease. Two cases were classified as recessive autosomal distal myopathy (Welander variant), two recessive autosomal (Miyoshi type), two autosomal recessive with rimmed vacuole (Myzuzawa and Nonaka type), and two as miscellany type.
Insights
This study examines eight distal myopathy cases, detailing symptom progression and diagnostic findings. It highlights the challenges in classifying these rare neuromuscular disorders based on current knowledge.
Area of Science:
- Neurology
- Genetics
- Pathology
Background:
- Distal myopathies are rare neuromuscular disorders with complex classification due to limited understanding of their pathogenesis.
- Accurate diagnosis and classification are crucial for effective patient management and therapeutic development.
Observation:
- Eight cases of distal myopathy (5 male, 3 female) were analyzed, with symptom onset typically in adolescence or early adulthood.
- Clinical presentation involved progressive muscle weakness, initially in distal lower limbs, then distal upper limbs, and finally proximal muscles.
- Diagnostic evaluations included serum enzyme levels, electromyography (EMG), and muscle biopsies, revealing varied patterns of myopathy and denervation.
Findings:
- Muscle biopsy results indicated features of myopathy and denervation, active chronic myopathy, or chronic myopathy.
- Specific histopathological findings included vacuoles with positive acid phosphatase and rimmed vacuoles.
- Elevated focal acid phosphatase in muscle fibers suggested its involvement in disease pathogenesis.
- Cases were sub-classified into Welander variant, Miyoshi type, Myzuzawa and Nonaka type, and miscellaneous types based on clinical and pathological features.
Implications:
- The findings contribute to a better understanding of the diverse clinical and pathological spectrum of distal myopathies.
- This case series underscores the need for comprehensive diagnostic approaches to classify these heterogeneous conditions.
- Further research into the pathogenesis, including the role of acid phosphatase, may lead to improved diagnostic criteria and targeted therapies for distal myopathies.