The cardinal symptom of this group of diseases is hypomagnesemia. The specific diseases of this group differ by severity and accompanying symptoms.
The extend of magnesium waste can by measured by clamp experiments in which serum magnesium has to be supplemented until steady state conditions have been established and serum concentration remains normal. All the other electrolytes have to be normalized too. In this steady state condition the renal loss can be quantified and related to oral or parenteral substitution.
Additionally, the following signs have to be considered: family history: autosomal dominant, recessive, x-linked, or de novo mutation; age of onset; accompanying symptoms: acid base disorders, disturbances in calcium balance, diarrhea or other hints about distrurbed enteral absorption; neurological symptoms: cramps, seizures, convulsion, tetany; hormonal disturbances: parathormon, glucagon, calcitonin, vitamin-D, ADH; intoxications: diuretics.
The loss of magnesium mainly occurs in the kidneys. The distal convoluted tubule reabsorbs the bulk of glomerular filtered magnesium. If enteral absorption is also altered, diarrhea may result. Hypomagnesemia can also develop in conjunction wit other electrolyte disturbances.
Dai LJ et al. (2001) Magnesium transport in the renal distal convoluted tubule.[^]
Konrad M et al. (2003) Recent advances in molecular genetics of hereditary magnesium-losing disorders.[^]