Atlantoaxial subluxation with recurrent consciousness disturbance in a boy with Lesch-Nyhan syndrome

Orthopaedic Manifestations of Inborn Errors of Metabolism

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Inborn errors of metabolism are disorders of carbohydrate, amino acid, organic acid, or purine and pyrimidine metabolism; disorders of fatty acid oxidation; disorders of metal metabolism; and lysosomal storage defects that can cause metabolic derangements that have secondary musculoskeletal effects.

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Orthopaedic surgeons should be aware that patients with inborn errors of metabolism may be at high risk for spasticity, which may cause joint subluxations, scoliosis, and contractures, as well as poor bone quality, which is caused by malnutrition or disordered bone growth.

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Multidisciplinary care and follow-up are important to identify musculoskeletal problems in a timely manner in order to provide effective treatment.

Macrocytic anemia in Lesch-Nyhan disease and its variants

Purpose

Lesch-Nyhan disease (LND) is an inherited metabolic disorder characterized by overproduction of uric acid and neurobehavioral abnormalities. The purpose of this study is to describe macrocytic erythrocytes as another common aspect of the phenotype.

Methods

Results of 257 complete blood counts (CBC) from a total of 65 patients over a 23-year period were collected from two reference centers where many patients are seen regularly.

Results

Macrocytic erythrocytes occurred in 81–92% of subjects with LND or its neurological variants. After excluding cases with iron deficiency because it might pseudo-normalize erythrocyte volumes, macrocytosis occurred in 97% of subjects. Macrocytic erythrocytes were sometimes accompanied by mild anemia, and rarely by severe anemia.

Conclusions

These results establish macrocytic erythrocytes as very common aspect of the clinical phenotype of LND and its neurological variants. Macrocytosis is so characteristic that its absence should prompt suspicion for some secondary process, such as iron deficiency. Because macrocytosis is uncommon in normal children, it can also be used as a clue for early diagnosis in children with neurodevelopmental delay. Better recognition of this characteristic feature of the disorder will also help to prevent unnecessary diagnostic testing and unnecessary attempts to treat it with folate or B12 supplements.

Normal uricemia in Lesch-Nyhan syndrome and the association with pulmonary embolism in a young child-a case report and literature review

Deficiency of hypoxanthine phosphoribosyltransferase activity is a rare inborn error of purine metabolism with subsequent uric acid overproduction and neurologic presentations. The diagnosis of Lesch-Nyhan syndrome (LNS) is frequently delayed until self-mutilation becomes evident. We report the case of a boy aged 1 year and 10 months who was diagnosed with profound global developmental delay, persistent chorea, and compulsive self-mutilation since the age of 1 year. Serial serum uric acid levels showed normal uric acid level, and the spot urine uric acid/creatinine ratio was >2. The hypoxanthine phosphoribosyltransferase cDNA showed the deletion of exon 6, and the boy was subsequently diagnosed to have LNS. He also had respiratory distress due to pulmonary embolism documented by chest computed tomography scan. This report highlights the need to determine the uric acid/creatinine ratio caused by increased renal clearance in LNS in young children. The presence of pulmonary embolism is unusual and may be the consequence of prolonged immobilization.

Genetic and mechanistic evaluation for the mixed-field agglutination in B3 blood type with IVS3+5G>A ABO gene mutation

BACKGROUND

The ABO blood type B(3) is the most common B subtype in the Chinese population with a frequency of 1/900. Although IVS3+5G>A (rs55852701) mutation of B gene has been shown to associate with the development of B(3) blood type, genetic and mechanistic evaluation for the unique mixed-field agglutination phenotype has not yet been completely addressed.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we analyzed 16 cases of confirmed B(3) individuals and found that IVS3+5G>A attributes to all cases of B(3). RT-PCR analyses revealed the presence of at least 7 types of aberrant B(3) splicing transcripts with most of the transcripts causing early termination and producing non-functional protein during translation. The splicing transcript without exon 3 that was predicted to generate functional B(3) glycosyltransferase lacking 19 amino acids at the N-terminal segment constituted only 0.9% of the splicing transcripts. Expression of the B(3) cDNA with exon 3 deletion in the K562 erythroleukemia cells revealed that the B(3) glycosyltransferase had only 40% of B(1) activity in converting H antigen to B antigen. Notably, the typical mixed-field agglutination of B(3)-RBCs can be mimicked by adding anti-B antibody to the K562-B(3) cells.

CONCLUSIONS/SIGNIFICANCE

This study thereby demonstrates that both aberrant splicing of B transcripts and the reduced B(3) glycosyltransferase activity contribute to weak B expression and the mixed-field agglutination of B(3), adding to the complexity for the regulatory mechanisms of ABO gene expression.

Variable morphology of the axis vertebrae in 100 specimens: implications for clinical palpation and diagnostic imaging

OBJECTIVE

The purpose of this study was to investigate and measure the variable morphologies of axis vertebrae and explore the clinical significance of variations as it may pertain to clinical palpation and diagnostic imaging.

METHODS

The common variable morphologies in 100 specimens of intact dry adult axis vertebrae (Chinese) were investigated and measured. The frequencies in deviation of odontoid processes, deviation of spinous processes, and presence of bifid spinous processes were observed. The distances between the apices of transverse processes and inferior articular facets were also measured.

RESULTS

Variable morphologies of C2 that we observed were deviation of odontoid processes (14 cases, 14.0%), deviation of spinous processes (3 cases, 3.0%), and bifid spinous processes (95 cases, 95.0%). Of the bifid spinous processes, 56 had a process on the left side equal to the right side, 21 were longer on the left, and 18 were longer on the right. The distances between apices of transverse processes and inferior articular facets in the left side of C2 were 17.67 +/- 2.47 mm, and that of the right side were 17.81 +/- 2.55 mm.

CONCLUSIONS

Because variable morphology of the axis is common, congenital deviation of the odontoid process, deviation of the spinous process, and asymmetrical bifid spinous processes should be taken into account during clinical palpation and diagnostic imaging.

Rare variant of Lesch-Nyhan syndrome without self-mutilation or nephrolithiasis

Lesch-Nyhan syndrome is a very rare X-linked recessive disorder characterized by mental retardation, spasticity resembling cerebral palsy, choreo-athetosis, self-mutilation and hyperuricemia. Self-mutilative behavior is a hallmark of the disease. Hyperuricemia leads to hyperuricuria and uric acid nephrolithiasis. The underlying defect is a deficiency of hypoxanthine-guanine-phosphoribosyl transferase. We report on a 7-year-old boy with Lesch-Nyhan syndrome, lacking self-mutilative behavior, who was erroneously diagnosed as having athetotic cerebral palsy. He also had no renal stones; hyperechoic renal medullary pyramids were the only renal abnormality detected and were sonographically indistinguishable from medullary nephrocalcinosis.