Bone metabolism disorders

Hypophosphataemic rickets

In this hereditary disease (also called “phosphate diabetes”), affected individuals excrete excessive amounts of phosphate through the urine. As a result, growing bones remain soft and deformed. The first signs of the disease can be seen as early as two to three months after birth. The anamnesis is followed by a blood pressure measurement, ECG and a hearing test. The height is also compared with the growth curve of healthy children.

The following symptoms can occur:

• Increased FGF23 serum level
• Curved legs and leg deformities (from the age of 2)
• Abnormal growth of the cranial bones
• Conspicuous head shape (asymmetrically long skull shape, lateral flattening, bulging forehead, widening of the bone sutures)
• Malalignment of the knee joints (X-/O-legs)
• Waddling, wide-legged gait
• Frequent bone fractures and pain
• Osteoarthritis due to bone malpositions
• Muscle weakness
• Shortened body parts
• Early growth retardation
• Impaired tooth development, tooth abscesses, paradontosis
• Sensorineural hearing loss

Possible diagnostic procedures:

• Determination of relevant serum levels (phosphate, alkaline phosphatase, vitamin D3)
• Urine tests
• Molecular biological tests
• Bone density measurement using DXA
• Determination of bone age by radiography
• X-rays
• MRT
• Sonography of the kidneys
• Heart echo (for people with high blood pressure)

Possible therapeutic measures:

• Medicinal (including for vitamin D metabolism, calcium, antibody build-up)
• Physical (treat muscle weakness, improve coordination and mobility)
• Surgical (take care of skeletal deformities)
• Orthopaedic (treat severe bone deformities)
• Dental treatments
• ENT treatments

Hypophosphatasia

Hypophosphatasia (also called “Rathbun’s syndrome”) is a rare, hereditary, non-curable metabolic disorder that is usually diagnosed in infancy and is caused by a genetic mutation. In hypophosphatasia, alkaline phosphatase (extremely important for bone formation) is insufficiently produced. The disease manifests itself in various ways, and the symptoms are non-specific. However, there are four types of hypophosphatasia, depending on age: perinatal, infantile, juvenile and adult. In the special form of odonto-hypophosphatasia, there is premature loss of the (milk) teeth.

The following symptoms may occur:

• Rickets-like symptoms (including waddling gait, x-/o-legs)
• Conspicuous short stature
• Recurrent fatigue fractures
• Poor healing of fractures
• Bone marrow oedema (abnormal accumulation of fluid)
• Muscle and bone pain
• Pathological remodelling processes in the bones
• Conspicuous early loss of milk teeth, maldevelopment of dentition
• Periodontosis, conspicuous problems with caries, tooth anomalies
• Pathological deposits in the joint, mineralisation of the joint cartilage, joint pain
• Tendonitis, calcification and adhesions, rheumatism
• Diarrhoea, constipation, malaise due to intolerances
• Depression, headaches, anxiety disorders, insensitivity
• Kidney stones, kidney weakness, insufficiency and calcification

Possible diagnostic procedures:

• Bone density measurement using DXA
• X-rays
• Bone scintigraphy
• MRT
• Nuclear medicine examinations
• Molecular biological examinations
  Laboratory tests (e.g. calcium, phosphate, vitamin B6)
• Examination of bone remodelling markers

It is also important to find out whether the patients have a thyroid disease, suffer from anaemia or bone malformations. Is there dangerous copper accumulation with associated functional disorders of the liver, central nervous system, eyes and/or kidneys (Wilson’s disease)? Is the vitamin deficiency disease scurvy also present? Can overweight operations be responsible for certain values? Is there a severe magnesium deficiency? Are certain contraceptives being taken?

Possible therapeutic measures:

A (long-term) enzyme replacement therapy replaces the alkaline phosphatase that is genetically missing. This therapy can alleviate many of the symptoms mentioned. Drug therapy with non-steroidal anti-inflammatory drugs, osteoporosis therapeutics and vitamin D is also possible. Heat or cold therapy and physiotherapy are also recommended.