Motor Axonal Neuropathy Associated With Idiopathic CD4+ T-Lymphocytopenia
A 10-year-old boy with no significant birth or family history was hospitalized in the pediatric ward of our hospital for recurrent respiratory infections. Per the patient's medical record, he exhibited normal development, though he was hospitalized at 16 months of age for pneumonia. Since that time, the patient was repetitively hospitalized for various infections, including pneumonia, otitis media, and paranasal sinusitis. Given these recurrent infections, an underlying immunodeficiency was suspected. A subsequent laboratory workup was performed, revealing normal serum quantitative immunoglobulin and complement levels as well as a marked decrease in CD4+ T cells. The patient was then diagnosed with idiopathic CD4+ T-lymphocytopenia at the age of 5, given his history of recurrent infections in the setting of a low CD4+ T cell count. All secondary infections were then conservatively treated with antibiotics, and the patient was closely followed as an outpatient, though immunotherapy was not performed.\nSeveral years later, in 2010, the patient complained of generalized weakness of his four extremities, although he reported that these symptoms did not significantly affect his daily life. However, as this limb weakness continued to worsen, the patient was then referred to our clinic in the Department of Rehabilitation Medicine in January 2011 for further evaluation and treatment. At the time of his first examination, the patient was 124 cm tall, weighed 19.4 kg, and had a body mass index of 12.36, which is defined as being underweight. Prominent muscular atrophy of the limbs was noted on the exam (). Using the Medical Research Council (MRC) scale, manual muscle testing was then performed revealing the following: upper extremity shoulder flexion 2/5, abduction 2/5, elbow flexion 3/5, extension 2/5, wrist flexion 3/5, and extension 2/5; lower extremity hip flexion 2/5, extension 1/5, knee flexion 1/5, extension 2/5, ankle dorsiflexion 1/5, great toe extension 3/5, and plantarflexion 2/5. All results were symmetric for the contralateral upper and lower extremities. Additionally, no sensory abnormalities were detected in temperature, tactile, position, or vibration sensation. The patient's deep tendon reflexes for the bilateral biceps and knees were also normal. During the entire exam, the patient was conscious and alert, and the cranial nerve examination was without abnormal findings. The patient was able to turn over in bed, but was unable to sit up from a supine position without assistance. In terms of the degree of independence in daily living, the patient had a Modified Barthel Index (MBI) of 28, indicating the need for maximal assistance from other people.\nA subsequent motor nerve conduction study showed decreased compound muscle action potential amplitude for the left median, ulnar, right peroneal, and tibial nerves, although the latency and nerve conduction velocity were within normal limits. Additional sensory nerve conduction studies were also within normal limits (). Needle electromyography further revealed increased insertional activity for all examined muscles, with a large amount of abnormal spontaneous activity noted in the paralumbar muscles, left vastus medialis, tibialis anterior, gastrocnemius, right biceps brachii, and abductor pollicis brevis. Specifically, polyphasic motor unit action potentials and reduced motor unit recruitment were observed during muscle contraction (). A somatosensory evoked potential study of the tibial nerve; however, it did not reveal any specific findings.\nResults from an additional electrodiagnostic study indicated that the motor nerves of the upper and lower extremities were primarily affected, with a marked reduction in compound muscle action potential amplitude in the setting of a normal conduction velocity pattern. The results suggested a major axonal involvement rather than a demyelinating process. A diagnosis of the motor axonal type was then reached, given the results from the sensory nerve studies and lack of associated clinical symptoms. A number of additional diagnostic studies were then performed in order to identify the underlying etiology of the process, with no significant finding noted on the magnetic resonance imaging of the brain, vertebrae, and cerebrospinal fluid (CSF). Serum muscle enzymes, electrolytes, thyroid function tests, and liver function tests were also within the normal range. Additionally, serum immunoglobulin GM1 and GD1 were both negative as was the antibody testing for all associated infectious diseases (e.g., HIV) and abdominal ultrasonography (). The patient was found to have a decreased number of CD4+ T cells on lymphocyte subtyping (). A sural nerve biopsy was not performed as the sensory nerve function was found to be normal in the electrodiagnostic study.\nClinically, the patient had significant difficulty in carrying out daily living activities, including walking, due to marked muscle weakness. Rehabilitation treatment focused primarily on wheelchair transfer training, joint contracture prevention, and posture maintenance, since active rehabilitation was not possible due to the patient's recurrent infections. As the pulmonary function testing showed decreased respiratory function, pulmonary rehabilitation was also initiated.