Boucher Neuhäuser Syndrome - A rare cause of inherited hypogonadotropic hypogonadism. A case of two adult siblings with two novel mutations in PNPLA6

Boucher Neuhäuser Syndrome (BNS) is a rare clinical syndrome with autosomal recessive inheritance defined by early-onset ataxia, hypogonadism and chorioretinal dystrophy. We present two siblings diagnosed with BNS in late adult life identified with compound heterozygous state of two novel PNPLA6 mutations. Five healthy siblings were non- or heterozygous carriers of the mutations. The cases, which presented with ataxia in childhood and hypogonadotropic hypogonadism (HH), were diagnosed at age 17 and 25, respectively, when examined for delayed puberty. The youngest case, a 55-year old male, was referred to our department in 2006 for evaluation of secondary causes of osteoporosis, which he developed despite adequate testosterone replacement therapy. The unusual medical history with childhood ataxia and hypogonadotropic hypogonadism lead to further examinations and eventually the diagnosis of BNS. The older sister of the proband also displayed the triad of ataxia, HH and chorioretinal dystrophy accompanied by cerebellar atrophy and in 2014, we found the mutations in PNPLA6. BNS is a rare cause of HH and secondary osteoporosis, but should be considered in patients presenting with one or more of the key features. Genetic screening is becoming increasingly available and inexpensive and accordingly this may be considered earlier and by broader indication in unusual phenotypic presentations. The increasing knowledge of causes for inherited diseases should extend the use of genetic screening, as the correct diagnosis will benefit the patients.

Genetics; Hypogonadism; PNPLA6 mutation; Phospholipases; Retinal dystrophies; Spinocerebellar ataxias.