Abstract
Two siblings of an achondroplastic father with radiological features of hereditary multiple exostoses are presented. This condition is rarely reported and there are few reports among black Africans. These two cases are reported to heighten the index of suspicion in diagnosis.
BACKGROUND
Hereditary multiple exostoses (HME) is a rare autosomal dominant disorder affecting the endochondral skeleton during growth.1,2 It is characterised by the development of benign tumours (multiple osteochondromas) which manifest as the diagnostic exostoses which grow out from the metaphyses of long bones. Though rare, its estimated prevalence has been put at 1 in 50 000 births. The presentation is variable.
Though the condition is usually asymptomatic, complications include bone pain, deformities, shortening of long bones, restricted motion of joints, and nerve and blood vessel compressions.2,3 Malignant transformation has been estimated in the order of 5% of all cases.3 Rare complications include cervical cord compression4 and affectation of the ribs with resultant haemothorax and pericardial effusion.5
HME is a genetically heterogeneous disorder and is associated with mutations in EXT 1 or EXT 2 genes, both of which are tumour suppressor genes.3 Compared with EXT 2 linkage, females with EXT 1 linkage have been reported to be, on average, smaller in stature. Also, persons with EXT 1 linkage and an as yet undetermined linkage [EXT?] are more severely affected and underwent further surgery.6
HME has often been reported among siblings and members of the same family.1,6 There has been only one documented report of HME in a black African family in Congo.7 There is no recorded case from Nigeria, hence this report of HME in two male siblings aged 5 and 8; both of whom are children of an achondroplastic father.
CASE PRESENTATION
MO and VO are, respectively, 5- and 8-year-old male siblings. Their father is 55 years old and achondroplastic; he is 4 feet 3 inches (1.3 m) in height and has short upper and lower limbs.
MO presented with a 2 year history of painless bony swellings in both lower limbs. The swellings had been increasing in size but there were no associated complications of pressure effects. The child had attained normal development milestones and is not small for his age. Radiography of the lower limbs show the multiple exostoses (figs 1 and 2).
Figure 1.
Five-year-old boy with multiple exostoses adjoining the knee joints.
Figure 2.
Multiple exostoses in the femur and tibia of a 5-year-old boy.
VO presented with a 5 year history of bony swellings of both the upper and lower limbs which had progressively increased in size. He had occasional bone pains in the upper and lower limbs which responded to treatment with non-steroidal anti-inflammatory drugs (NSAIDs). Radiography showed multiple exostoses in the lower limbs (fig 3 and 4) and the upper limbs (figs 5 and 6).
Figure 3.
Multiple exostoses in the lower limbs of an 8-year-old boy.
Figure 4.
Multiple exostoses in the lower limbs of an 8-year-old boy.
Figure 5.
Multiple exostoses in the right forearm of an 8-year-old boy.
Figure 6.
Exostoses in the left arm of an 8-year-old boy.
Both boys are both being followed up and there have been no signs of any of malignant transformation or any other complication.
DISCUSSION
The two cases presented are siblings of the same father and mother. Their ages at presentation were 5 and 8 years, respectively. It has been observed that HME is rarely present at birth but develops gradually and may persist to grow slowly after growth plates closure.8 Radiological manifestations start at the age of 4–5 years. Both cases have exostoses located in the legs, especially around the knees. The face is not usually affected. This is in keeping with previous observations.9 Both cases presented are boys, which are in keeping with previous reports of male preponderance. Pain is a major complaint in those affected, as evidenced by the bone pain present in one of the subjects. In a questionnaire survey of 293 subjects with HME, it was reported that 84% of the respondents had pain of which 55.1% was generalised.10 It was also found that individuals with HME related complications were five times more likely to have pain while those who had surgery were 3.8 times more likely to have pain.
One other major concern with HME is malignant transformation. Surgical resection has therefore been suggested to pre-empt this, as well as to prevent deformities.11
LEARNING POINTS
Hereditary multiple exostosis (HME) is a rare disease, and is rarely reported in black Africans.
Two siblings with HME are presented, both of whom are children of an achondroplastic father.
Footnotes
Competing interests: none.
Patient consent: Patient/guardian consent was obtained for publication
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