Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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May 14, 2020
Unilateral Kallmann Syndrome with Associated GM Heterotopias
- Background:
- Kallmann syndrome (KS) is a congenital condition that arises due to impaired migration of olfactory axons and gonadotropin-releasing hormone (GnRH) neurons from the embryonic olfactory placode to the hypothalamus, resulting in olfactory bulb/tract hypoplasia/aplasia and malformations of the basal frontal cortex. It is considered in the spectrum of neuronal migration anomalies.
- KS most commonly presents as a bilateral defect, but rarely can be unilateral, as in this case; both present with anosmia/hyposmia and gonadotropic abnormalities.
- The diagnosis of KS is made primarily by meeting clinical/hormonal criteria, but can be supported by imaging.
- Clinical Presentation:
- Most commonly presents in men, with cryptorchidism, microphallus, and lack of pubertal changes (virilization, voice deepening, growth spurt, body hair development); women present with primary amenorrhea, lack of body hair and breast development
- Both sexes can present with congenital abnormalities (hyposmia/anosmia, midline defects, unilateral renal agenesis).
- Biochemical analysis reveals inappropriately decreased FSH/LH levels, a decreased testosterone level in men, and decreased estradiol levels in women.
- Key Diagnostic Features:
- MR imaging demonstrates agenesis/hypoplasia of olfactory bulbs and tracts and a decrease in depth or absence of the olfactory sulcus resulting in a lack of clear differentiation between the gyrus rectus and the medial orbital gyrus.
- Ethmoid bone flattening can be present on CT.
- Differential Diagnoses:
- Constitutional delay of growth and puberty: can appear similar to KS with an uncharacteristically low GnRH concentration, but imaging does not reveal causative brain abnormalities; is a diagnosis of exclusion and tends to run in families in an autosomal dominant fashion
- Pituitary/hypothalamic lesion: can cause central hypogonadism; however, focal lesions of the pituitary, infundibulum, or hypothalamus are not part of the etiology of KS
- Prader-Willi syndrome: clinical symptoms can appear similar to KS (obesity, short stature, delayed puberty, hypogonadism); however, imaging displays no specific findings that aid in this diagnosis.
- Treatment:
- Hormone replacement therapy for both men and women
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