Bone diseases
that lead to false allegations of non-accidental injury
By Dr. Colin Paterson
Extract of Dr Colin Paterson's lecture at the NCHR's Symposium, under
the theme "Corruption and miscarriages of justice in child care
cases" (Rättsröta och myndighetsmissbruk i barnavårdsärenden), which was held at Hotel
Europa,
|
This extract is published here with the kind consent of
the lecturer/author. |
The investigation of children in whom abuse is
suspected includes a search for fractures.
The finding of fractures, particularly fractures of the ribs and
fractures at the ends of long bones (metaphyseal fractures), may be taken as
evidence of non-accidental injury. This
view is strengthened if the x-ray appearances suggest that the fractures are of
different ages. If the parents or carers
of the child deny causing injury, it may be assumed that they are lying or
covering up for someone else.
However, several bone disorders may also cause
fractures to occur, apparently spontaneously or with normal handling, and
unexplained fractures of whose presence the parents were unaware may be found
on routine radiology. This presentation
will outline these disorders and indicate the diagnostic clues that may be
helpful. One frequent feature common in
all of these disorders is the finding that superficial evidence of trauma is
not commensurate with the number or types of fractures found on x-ray.
The principal disorders known to cause unexplained
fractures and difficulty in diagnosis are:
Osteogenesis imperfecta
Temporary
brittle bone disease
Bone
disease of prematurity
Rickets
due to vitamin D deficiency
Scurvy
(vitamin C deficiency)
Copper
deficiency and Menkes’ syndrome
This condition, often known as brittle bone disease,
has been recognised for over a century.
In recent years, it has become clear that most, but not all, cases are
caused by genetic defects in the genes coding for collagen, the principal
structural protein of bone and of other parts of the body. This protein is essential for the mechanical
strength of bone. Although
conventionally five distinct types of osteogenesis imperfecta are described,
the reality is that there are many hundreds of different genetic defects. There is similarly great variation in the severity
and clinical features of the condition.
Some individuals are so severely affected that stillbirth or early
neonatal death is inevitable. At the
other extreme are people who have few or no fractures but yet are undoubtedly
affected on the basis of family history or genetic investigation.
In many individuals osteogenesis imperfecta is
inherited from one or other parent. The
child of an affected parent has a one in two chance of being affected. ‘New mutations’ (new cases arising without
any family history) are common.
Clinical features of osteogenesis imperfecta may
include blue or grey colour of the sclerae (whites of the eyes), discoloration
or fragility of the teeth, laxity of the joints, an increased tendency to
bruising or pinpoint bruises known as petechiae. Deafness may occur in the teenage years or
early adult life. Very few patients show
all these features and some, undoubtedly affected, show none of the clinical
features apart from fractures.
Fractures of all types occur in osteogenesis
imperfecta. These include transverse,
oblique, spiral and metaphyseal fractures of long bones, skull fractures, rib
fractures and spinal fractures.
Fractures may occur with little or no recognised force and fail to occur
on other occasions when they might be expected.
There is no consistent pattern to the fracturing; in many individuals
there are long fracture-free periods.
X-ray appearances of the bone may be abnormal. However, in many patients, the bones appear
normal at the time when the first few fractures are recognised. Measurements of
bone mineral density often give normal results.
Routine biochemical tests for, for example, blood calcium, phosphate and
alkaline phosphatase levels are generally normal. However specialised laboratory investigations
may help in diagnosis. One test involves
taking a skin biopsy, culturing the fibroblast cells and examining the collagen
produced. Another test involves
examining the DNA obtained from a blood sample.
Neither test shows abnormalities in all patients with osteogenesis
imperfecta.
Our research and that of others over the last
nineteen years has provided evidence for the distinct variant to which we have
given the name temporary brittle bone disease.
This work remains very controversial and some have said that the
disorder does not exist. However, we
have increasingly good evidence that our work is accurate although the cause of
the condition is not yet known.
In this disorder the fractures are limited to the
first year of life and, to a large extent, the first six months of life. There may be very large numbers of fractures,
particularly fractures of the ribs and metaphyseal fractures. Other clinical features in some cases include
vomiting, which may be projectile, and anaemia.
The family history may include joint laxity in one or other parent. The condition is common in children born
pre-term and in twins. One risk factor
appears to be diminished fetal movement in late pregnancy.
It is important to note that metaphyseal fractures
(‘chip fractures’, ‘corner fractures’,
‘bucket-handle fractures’) are not specific for
non-accidental injury but have a wide range of causes in addition to
osteogenesis imperfecta and temporary brittle bone disease.
Four factors contribute to the view that temporary
brittle bone disease is a real entity and not misdiagnosed non-accidental
injury. First, the patients have many
similarities both clinically and radiologically. Second, there is usually a substantial discrepancy
between the radiological evidence of fractures and the clinical evidence of
trauma. Third, the same syndrome occurs
in situations in which non-accidental injury can be excluded with some
confidence. Fourth, in over 70 patients
returned to their parents there has been no subsequent evidence of physical
abuse.
It has been known for many years that fractures,
including spontaneous fractures, can occur in infants born before
full-term. The fractures particularly
include rib fractures and metaphyseal fractures but can occur at any site. Most published descriptions of the fractures
in this condition report fractures limited to the first six months of life.
The cause of the disorder is not known. While it is often called rickets, there is no
evidence that it is caused by lack of vitamin D. A number of tentative suggestions have been
made including lack of the period of activity in late intra-uterine life which
appears to be important for bone formation.
It is not yet possible to delineate this disorder from temporary brittle
bone disease.
Radiological signs sometimes include apparent
diminution in bone density. Laboratory
tests sometimes show a high blood level of the enzyme alkaline phosphatase.
Vitamin D is obtained partly from exposure to
ultraviolet light and partly from a rather limited range of foodstuffs. In
In most cases the radiological appearances help to
make the diagnosis but not all patients show abnormality. Abnormal blood tests may include low levels of
calcium or phosphate, high levels of alkaline phosphatase, increased levels of
parathyroid hormone and low levels of the major form of vitamin D in blood,
25-hydroxyvitamin D. While fractures
have long been recognised as a feature of rickets, x-rays may also show
fracture-like appearances known as pseudo-fractures or Looser’s zones. These can be misinterpreted as fractures.
Vitamin C is essential for the formation of collagen
and is obtained mainly from fruit and vegetables. In infancy vitamin C deficiency may cause
fractures, periosteal reactions and metaphyseal abnormalities. Clinical features may include bruising and
bleeding from the gums. Intracranial
bleeding may occur. Laboratory
investigations for vitamin C lack are not very satisfactory and the condition
is probably under-diagnosed.
Copper has an essential role in the formation of
collagen. Lack of copper for any reason
may cause a condition similar to temporary brittle bone disease. Recognised causes of copper deficiency
include pre-term birth and prolonged periods of parenteral feeding but the
cause is not always obvious. The
investigation for this condition is unsatisfactory. Copper levels in blood may be misleading in
not reflecting the copper stores in the body.
Menkes’
syndrome is a rare genetic disorder occurring in male children who suffer
neurological deterioration and seldom survive beyond the age of three. It is an inborn defect in copper metabolism
and, as with copper deficiency, spontaneous fractures may occur.
Colin R Paterson May
2004
Division of Medicine and Therapeutics
Reports/gothenburg abstract 2004
Relevant publications
1.
2.
3.
4.
5.
6.
Miller M E. Temporary brittle bone disease: a true
entity? Semin Perinatol 1999; 23:
174-82.
7.
Miller M E. The lesson of temporary brittle bone disease:
all bones are not created equal. Bone 2003; 33: 466-74.
1.
Ablin, D S, Greenspan A, Reinhart
M, Grix A. Differentiation of child
abuse from osteogenesis imperfecta. AJR 1990; 154: 1035-46.
2.
Chapman S, Hall C M. Non-accidental injury or brittle bones. Pediatr
Radiol 1997; 27: 106-10.
The
child with unexplained fractures
By Colin Paterson
La Maladie des os de verre -
Deux cas Français
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