Saudi experience with classic homocystinuria

Tracheobronchomegaly (Mounier-Kuhn syndrome) and Bronchiectasis as rare manifestations of Homocystinuria

Homocystinuria (HCU) is a rare autosomal recessive inherited disorder usually diagnosed in childhood. It is characterized by a deficiency of the enzyme that converts homocysteine to cystathionine. The accumulation of homocysteine leads to abnormalities in the ocular, skeletal, cardiovascular, and central nervous systems. HCU shares several clinical features with Marfan syndrome; however, respiratory system involvement in HCU is uncommon and rarely reported. Bronchiectasis has been previously reported in a few cases of HCU, and it was attributed mainly to fibrillin deficiency. This case describes a young girl diagnosed with classical HCU since childhood who presented with a chronic productive cough and was initially misdiagnosed as bronchial Asthma. However, upon further evaluation, she was eventually diagnosed with tracheobronchomegaly (TBM), or Mounier-Kuhn Syndrome, and bronchiectasis based on the computed tomography (CT) scan of chest findings. To our knowledge, this is the first reported case of TBM and bronchiectasis in HCU. We believe that fibrillin degeneration may be the key to understanding this unusual association in HCU.

Neurodevelopmental and Cognitive Outcomes of Classical Homocystinuria: Experience from Qatar

BACKGROUND

Classical homocystinuria due to cystathionine β-synthase (CBS) deficiency (OMIM 236200) is a recessively inherited condition caused by mutations in the CBS gene. The founder mutation p.R336C accounts for almost all CBS deficiency in Qatar, affecting approximately 1 in 1,800 births, making it the most prevalent monogenic disease among the Qatari population. Untreated patients can have severe intellectual disability (ID), devastating multisystem complications and premature death. Current treatment is based on pharmacology therapy and life-long methionine-restricted diet, which is difficult to maintain particularly in late diagnosed individuals. Data on the neurodevelopmental and psychological impact of the disease on outcomes among Qatari patients are generally lacking and have not been studied.

OBJECTIVES

To examine the cognitive, educational and psychological outcomes of classical homocystinuria on Qatari patients.

SUBJECTS AND METHODS

Thirty-two cases with classical homocystinuria and 25 sibling controls were recruited to evaluate the neurodevelopmental and cognitive outcomes. We reviewed the subjects' medical record and collected pertinent clinical and educational data from parents. Stanford-Binet Intelligence Test (Arabic translation - 4th ed.) was used for cognitive (IQ) testing.

RESULTS

The mean age for the subjects was 11.2 years (range 0.6-29) with 56% males. The majority of cases (93%) carried the mutation (p.R336C), and parental consanguinity was 84%. There were no differences between the two groups in the fine motor, expressive language, behavioural and visual skills. However, cases have much lower total IQ particularly in the domains of short memory, quantitative reasoning and visual-spatial domains. A significant number of adolescents and adult cases had medical co-morbidities as well as behavioural and emotional problems.

CONCLUSION

Individuals with classical homocystinuria have many developmental and cognitive difficulties with significant number of cases having learning disability and lower IQs (cf. sibling controls) with adolescents and adults more affected. Those diagnosed by newborn screening have better developmental and cognitive outcomes compared to late diagnosed cases. Psychological and psychiatric referrals should be part of the standard of care for those cases.