Diagnosis and clinical approach in Gitelman's syndrome

Hypokalemia, defined as a plasma potassium concentration <3.5 mmol/l, is the most common electrolyte abnormality encountered in our clinical practice. Unfortunately, in many cases, the etiologies were unclear and resulted in a wrong treatment. Indeed, the true etiology could be such a 'rare' one and could be found by doing a comprehensive work up. One of this is Gitelman's syndrome, a rare genetic disorder characterized by hypokalemic alkalosis, hypomagnesemia, hypocalciuria, and secondary aldosteronism without hypertension. Since this disorder is found in 1% Caucasian populations, this is one of the most frequently inherited renal tubular disorders. A 27 year old man came to emergency room with weakness and generalised muscle cramps. He was investigated three months before for a similar electrolyte disturbance which was found to be inconclusive. The routine laboratory data in emergency room revealed a potassium concentration of 2.3 mmol/l. He had never used diuretics or hormonal therapy nor had history of vomiting or diarrhea. He had normal blood pressure and the blood gas analysis revealed metabolic alkalosis. On his ECG (electrocardiography), we found the prominent U wave. Despite his low concentration of serum potassium and cloride, the concentration of these electrolytes in urine were extremely high. We also found hipomagnesemia. The calcium concentration in serum was normal with slightly hypocalciuria. Even with aggressive oral and intravenous potassium suplementation, the patient remained hypokalemic. In cases when the etiology of hypokalemia is unclear, we should perform some investigations to confirm the diagnosis and give the proper treatment. In Gitelman's syndrome, where the defect in the distal tubule cannot be corrected, the treatment must be a life-long. Most patients require oral potassium and magnesium supplementation, since drug therapy is usually incompletely effective.

Clinical features of spondyloarthropathy in Chinese and native Indonesians

The prevalence of spondyloarthropathy (SpA) in Chinese Indonesians is much higher than in native Indonesians. This is due to HLA-B27 subtype differences. In the present study we re-examined the clinical features of SpA in Indonesians to see whether, besides the HLA-B27 subtype differences, other factors affect the frequency of SpA. Seventy two patients with SpA were re-examined. The patients came from two clinics for rheumatic diseases. The overall entry ratio of Chinese to native Indonesians was 1:2. Ankylosing spondylitis (AS) was more frequent among the Chinese (n = 32, 94% B27 positive) than among the native Indonesians (n = 5, 40% B27 positive). HLA-B27 subtyping was performed on 22 of the 37 HLA-B27-positive AS patients. Twenty Chinese were positive for B*2704 and two native Indonesians were B*2705 positive. The clinical features of AS and reactive arthritis (ReA) showed no differences between the two populations and were similar to the clinical descriptions in other parts of the world. In conclusion, it can be stated that in spite of HLA-B27 subtype differences the clinical features of SpA in Chinese and native Indonesians are fully comparable.

HLA-B27 subtypes positively and negatively associated with spondyloarthropathy

OBJECTIVE

Eleven subtypes of HLA-B27 have been identified. If some of these subtypes had a stronger association with spondyloarthropathy (SpA) than others, this might tell us which peptides are of pathogenetic importance. A subtype preponderance has not been proved in Caucasians or in Asian Indians. Our objective was to determine whether some subtypes are positively or negatively associated with SpA in Indonesia.

METHODS

Cells of 34 HLA-B27 positive patients with SpA (fulfilling the European Spondylarthropathy Study Group criteria) and 26 HLA-B27 positive controls, all living in Java, Indonesia, were sampled. Patients and controls were divided according to their presumed ethnic origin. HLA-B27 subtyping (B*2701-09) was performed by polymerase chain reaction in combination with sequence specific oligonucleotide probes to analyze polymorphism in exons 2 and 3 of HLA-B27.

RESULTS

HLA-B*2701, *2702, *2703, *2708, and *2709 were found in neither group. HLA-B*2704 was found in 23/34 (68%) of the patients and in only 4/26 (15%) of the controls (p < 0.01). HLA-B*2706 was found in none of the 34 patients, but in 21/26 (81%) of the controls (p < 0.01). One drawback of the study was that most patients were of Chinese descent and most controls were native Javanese. Nevertheless, the absence of SpA among HLA-B*2706 positive individuals is noteworthy.

CONCLUSION

HLA-B*2704 is positively associated with SpA (RR = 11.5), while *2706 is negatively associated with this disease (RR < 0.007). The results confirm the findings of Lopez-Larrea, et al in Thailand.