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X-linked spinal and bulbar muscular atrophy (SBMA or Kennedy's disease) has a variable prognosis. Most male carriers are affected by their fourth or fifth decade of life, while some remain asymptomatic lifelong. Elevations of serum creatine kinase are well known to occur in clinically manifesting SBMA patients. Elevations prior to the onset of the clinical syndrome have not been reported. Here we report two cases of SBMA presenting with 'idiopathic' elevations of serum transaminases and creatine kinase a decade in advance of their symptomatic onset. These cases emphasize the need to consider SBMA and genetic testing for the androgen receptor trinucleotide CAG expansion in males otherwise healthy with 'idiopathic' elevated creatinine kinase.

Mild to moderately elevated creatine kinase (CK) activity is a frequent biochemical finding in proximal spinal muscular atrophy (SMA). In a collaborative study on all types of childhood and juvenile onset SMA, we analysed the CK activity of 504 SMA patients (138 type I, 127 type II, 144 type IIIa, and 95 type IIIb patients). Under the assumption of a lognormal distribution of CK activity as the most appropriate statistical model, CK levels were transformed into logarithms and compared by standard deviation scores = CK-SDS (log). CK activity was statistically different between early and later onset SMA: in SMA I and II, about one-third of patients showed CK-SDS (log) >2 SD, the analysis of the means did not show significant differences. In SMA III, CK-SDS (log) was significantly higher (p < 0.01) than in the two other groups, which was most pronounced in SMA IIIb. More than 90% of SMA IIIb patients showed CK-SDS (log) values >2 vs. 57% in SMA IIIa. As similar values were obtained for a subgroup of 100 patients in whom the diagnosis of autosomal recessive SMA was confirmed by a deletion of the telomeric copy of the survival motor neuron gene, our results can be considered representative for SMA I-III. There was no correlation between CK level and disease duration. The fact that patients were ambulatory or chair-bound had no influence on CK activity in type III SMA. There was no sex influence in SMA I, II and IIIa. The observed higher male values in the group SMA IIIb are most likely the result of a lack of female patients with onset after puberty.

The medical records of 31 patients (19 male and 12 female) with clinical and electrophysiologic features of Wohlfart-Kugelberg-Welander syndrome were reviewed. The reported age at onset ranged from less than one year to 46 years, and the age at diagnosis ranged from three to 66 years. Proximal muscle weakness, especially of the lower extremities, and muscular atrophy were the predominant clinical features. Elevated serum creatine kinase levels were noted in four female and 12 male patients, and the degree of elevation was higher in the male patients (up to 32 times the upper limit of normal) than in the female patients. On initial evaluation, two patients were wheelchair-bound, whereas the others were ambulatory. On follow-up evaluation three to 32 years later (mean, 15.5 years), 11 patients used wheelchairs, although only three were wheelchair-bound. The disease followed a steady, slowly progressive course. The outcome of ambulatory status did not correlate with the initial creatine kinase determination.